Introduction

The contemporary Euroleague Basketball (EB) era started in 2000, and it was the highest-level professional men’s basketball league in Europe to remove restrictions on foreign players’ quotas. Available research up to that moment revealed that quantitative discrepancies between the NBA and EB had diminished and are continuing to reduce, which could have contributed to the tournament being more competitive [1, 2]. It is increasingly difficult to deny that the globalization of sports contributes to the creation of favorable conditions for players and boosts interest in other countries in international sports [3].

The NBA, the most competitive basketball league, has seen a sharp rise in foreign players over the past 20 years, which may have impacted changes in the European and other player markets [4]. Although the migration of athletes can be viewed as positive, there are some issues with it. Due to the tendency for athletes from other nations to be invited to compete effectively in international events, nationality and allegiance are now less significant than athletic prowess and aptitude [3]. According to the squad that best matches their playing style and financial benefits, players frequently switch teams, nations, and continents [5]. Local teams with access to international players could not be motivated to support local athletes, which would be detrimental to the growth of the national sports system. Talent development and identification in professional clubs and national governing institutions are two of the most important topics of discussion currently in adolescent team sports, since they establish the groundwork for future success and performance in senior sports [6, 7]. Due to the numerous subjective variables that scouts and coaches use to choose one player over another, team player recruitment has received critical attention [7]. Why local talent does not satisfy the needs of local teams is an understudied and important subject, with the primary goal of determining the true impact of domestic players on EB teams.

Recent innovations in EB have increased the necessity for objective variables to be evaluated through performance analysis. Understanding basketball players’ performance profiles is critical for clubs looking to optimize player scouting and recruitment in the local and worldwide markets. Previous research has focused on game-related statistics in an attempt to understand what variables are important for effective performance [8]. In fact, there have been recently some attempts to determine which variables contribute the most to differences in game starters and nonstarters [9], on factors that differentiate winning and losing teams [10, 11], the impact of rule changes [12], and the effect of home advantage in basketball games [13, 14]. For example, Ozmen [15] directly compute the marginal contribution and found that the most significant effect on the game was related to turnovers. Yu et al. [16], identified the most relevant technical performance variables, including points per game, field goals made, rebounds, assists, turnovers, blocks, fouls, and steals. Metulini & Le Carre [17] also calculated shot-scoring probabilities in relation to a set of game covariates related to game pressure. Despite the existing statistical links, the data’s rationale is somewhat contentious due to the players’ psychological, physical, and anticipatory skills [18]. Therefore, performance indicators remain more as an outcome of the game which is specific of a group or population. Furthermore, no research has been identified that assessed what contributions from domestic and international players lead to a better outcome in the EB. Recent research explored the differences in game-related statistics between national and foreign female basketball players in the women’s EB, according to playing positions and team ability [19]. The findings revealed that foreign athletes exhibited superior performance in metrics associated with offensive plays, while their national counterparts excelled in indicators linked to defensive actions. This phenomenon parallels certain observations in men’s basketball, where foreign players have consistently outperformed domestic athletes across multiple seasons within the Turkish Basketball League [15]. The examination of technical and physical distinctions between domestic and international soccer players was also investigated and categorized based on playing positions within the China Super League [20]. However, it is essential to note that these analyses in both basketball and soccer may not provide a comprehensive understanding. This limitation arises because these studies were conducted in leagues where tournament regulations-imposed restrictions on the number of foreign players. The constraint of foreign player limits can exert a significant influence, influencing not only the recruitment of high-caliber international athletes but also the promotion of local talents by affording them increased playing opportunities. In the context of football, specifically the UEFA Champions League, where there are no restrictions on player affiliations, it has been observed that teams composed of foreign players exhibit a home advantage effect in terms of goal scoring, while domestic players demonstrate a comparable goal-scoring performance both at home and away venues [21]. These studies thus far have shed light on the influence of including both national and foreign players on the overall performance of sports teams. However, to the best of our knowledge, there exists no prior research that quantifies the statistical contributions of foreign and domestic players in men’s EB. Beginning with the 2016–2017 season, EB adopted a new format, wherein all 18 teams participate in 34 regular season games. A more comprehensive analysis and discussion are warranted, as they could aid team managers, coaches, scouts, and performance analysts in more effectively evaluating the contributions of domestic players within the context of this elite basketball tournament. Consequently, the objective of this study was to examine performance disparities between national and foreign players in EB.

Materials and methods

Design

Data concerning player profiles and game-related performance were obtained from the official EB basketball website (https://www.euroleaguebasketball.net/euroleague/) which is consensually considered reliable [18]. To ensure the validity and applicability of this data for our study, we undertook a meticulous process of data verification, including cross-referencing with secondary sources and rigorous data cleaning procedures to correct any discrepancies, enhancing the overall reliability and accuracy of our analysis. The collected variables included match performance (MP) profiles (Table 1) such as minutes (Min), points (Pts), three-point percentage (3P%), two-point percentage (2P%). Calculations on a data set representing advanced basketball statistics were also used as performance indicators. To create our data set, we performed a different calculation using the following equations [22, 23]: percentage of total plays completed (Usage%) = Plays/Team plays, where Plays = Field goals attempted + FT possessions + Turnovers; Offensive rating (Off R) = (points scored/possessions) * 100 where possessions = plays—offensive rebounds, Defensive Rating (Def R) = (points allowed/possessions allowed) * 100 where possessions allowed = plays allowed—offensive rebounds allowed; True Shooting percentage (TS%) = Points / 2* (Field goals attempted + FT possessions); Assist percentage (AST%) = assists/ team field goals attempted + FT possessions, Offensive rebound percentage (ORB%) = Off rebounds/Team off rebounds + Team def rebounds allowed, Defensive rebound percentage (DRB%) = Def rebounds/Team def rebounds + Team off rebounds allowed; Fouls received rate (Fr rate) = fouls received/possessions.

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Table 1. Performance related variables.

https://doi.org/10.1371/journal.pone.0306240.t001

Results

The results of match performance are presented in Table 2. We found differences between local and foreign players in the following variables: Minutes (p = <0.001, ES = -0.402), Points (p = <0.001, ES = -0.743), Avg. Points (p = <0.001, ES = -0.915), Usage% (p = <0.001, ES = -0.402), Ind Off R (p = <0.001, ES = -0.327), Ind Def R (p = 0.016, ES = 0.203), TS% (p = 0.032, ES = -0.138).

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Table 2. Comparison of match performance between national and foreign players.

https://doi.org/10.1371/journal.pone.0306240.t002

Discussion

The primary aim of this study was to investigate performance disparities between NP and FP in EB. To the best knowledge, there are no studies examinating the player performance in EB based on advanced statistical analysis, as illustrated in Table 2. Our analysis suggests significant contrast in playing time between NP and FP, substantiating the presence of differences. This bias becomes evident through the unequal distribution of playing time within the preeminent European tournament. As Poli & Besson [24] have argued, the international migration of athletes has emerged as a noteworthy aspect of globalization within the sports industry. The allocation of minutes on the court further accentuates the profound influence that FP exert on the competitiveness of EB clubs. Concurrently, this raises a conspicuous concern for FP: the physical workload they endure is nearly twice that of their local counterparts.

During a single regular season in European EB, our analysis indicates a notable disparity (p < 0.001) in the accumulation of TPts scored by individual players, with FP showing significantly superior scoring performance when compared to their NP counterparts. Previous research in the realm of basketball player success has primarily emphasized scoring abilities, often regarded as a pivotal component in player profiling [25, 26]. While previous studies have often focused on scoring abilities as key to basketball player success, our findings suggest a correlation between player origin and scoring, with FPs typically achieving higher total and average point values.

Prior studies have already established the substantial influence of FP on scoring within national competitions [9, 27]. Nevertheless, it’s essential to acknowledge that the EB competition operates at a distinctive level, and the selection of players for this league sets unique standards that may not be universally applicable.

Oliver’s [23] Ind Off R quantifies the points a player has scored in a hypothetical 100 possessions. This statistic, while not indicative of the pace of play, serves as a quantitative measure that effectively distinguishes between FP and NP, with a significance level of p < 0.001. Furthermore, it sheds light on the offensive creativity displayed by the players, as highlighted by Memmert [28]. It’s important to note that Ind Off R is not tailored exclusively to taller players and holds greater relevance for proficient three-point shooters. Nonetheless, these statistics enable us to characterize FP as skilled long-range shooters, even within the sample group that includes taller players, who typically operate closer to the basket.

The purpose of calculating the Ind Def R is to assess a player’s ability to prevent their opponent from scoring individually. Our collected data reveals that FP allow opponents to score fewer points compared to NP, with a significance level of p<0.016. This finding contradicts earlier studies, which have suggested that foreign players are typically recruited for offensive roles, while national players are predominantly utilized for defensive purposes [27]. Furthermore, our research aligns with previous studies indicating that achieving high offensive and defensive ratings in a regular season is an uncommon occurrence among basketball players [8, 29]. Our study distinguishes foreign players in the Euroleague tournament as characterized by versatility, exhibiting both offensive and defensive proficiency. Recent research further supports the notion that the EB tournament emphasizes player versatility, a quality that has long been esteemed in the NBA [1, 2].

Conclusion

Our study provides an in-depth analysis of the distinct performance metrics of foreign and national players in Euroleague Basketball, revealing that foreign players often excel in key areas such as playing time, total points, and average points per game. This challenges the traditional perception of foreign players being mainly offensive, highlighting their diverse contributions. However, it’s important to recognize that these insights are specific to the Euroleague context and may not extend to other basketball leagues with different standards and styles of play. Therefore, while our findings offer valuable considerations for team scouts and player managers in the Euroleague, we caution against a broad application of these results to other settings.