Evaluating the state of player development in Major League Soccer during the youth-to-senior transition process

Mannix, P (2025) Evaluating the state of player development in Major League Soccer during the youth-to-senior transition process. Doctoral thesis, Liverpool John Moores University.

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Abstract

A pivotal moment in a soccer player’s career is the transition from the youth academy (YA) to the first team (FT), a period marked by uncertainty, greater psychological and physiological demands, and both an evolving status and identity within the hierarchy of a professional club. While player development systems, such as YA programmes, in professional soccer have become more sophisticated, the youth-to-senior transition still poses major challenges for club stakeholders charged with successfully progressing talented young players into FT soccer. Traditionally explored by sport psychology scholars through qualitative research methodologies and within British and European contexts, this within-career transition is now receiving growing attention and interest globally from various club stakeholders, such as coaches and applied sport science practitioners, aiming to understand the physical and organisational demands associated with the transition process into professional FT environments. In North America, Major League Soccer (MLS) has experienced rapid expansion, significant investment in homegrown player development initiatives, the installation of professional reserve teams (RT), and the establishment of a third-tier developmental league, MLS Next Pro (MLSNP). These strategic efforts have aimed to foster a more cohesive ‘professional player pathway’ (PPP), yet the structural evolution of MLS has created a complex player development system. Therefore, the aim of this thesis was to assess the state of player development in MLS during the youth-to-senior transition process

The aim of the first study (Chapter 4) was to survey MLS stakeholders’ attitudes and perspectives on the youth-to-senior transition, gathering insights on [1] the organisational aims and structure within MLS clubs, [2] the capabilities of club entities (i.e., RT and YA) to prepare players for the FT, and [3] the overall transition process within MLS. A total of 80 participants working in various ‘player operation’ roles for MLS clubs voluntarily completed an online survey. The results demonstrate that MLS has joined the global game by adopting a club structure model, involving YAs and RTs that aim to develop young professionals for the FT. The key decision-makers determining players’ upward mobility within MLS organisations are technical staff and club executives. Though, while players are transitioning into the professional FT, communication may or may not always be clear and effective, and psychological support may be absent, which may impair player development initiatives set by individual clubs and MLS more broadly.

The aim of the second study (Chapter 5) was to explore MLS homegrown players’ within-career transition experiences to understand the state of player development during the transition process to FT soccer. An explanatory sequential mixed methods design was employed, beginning with a quantitative analysis of match data from 397 professional and youth international games, followed by semi-structured interviews with 10 youth international players (mean age = 18.3; ± 0.48 y), who were under contract with MLS clubs. A deductive-inductive thematic analysis revealed five main themes: strategic club operations, gaining competitive experience, competition program standards, supplemental federation support, and environmental change outcomes. The results from this study illustrate the complexities of within-career transitions, emphasizing defined talent pathways, adaptability, and support mechanisms in player progression, providing valuable insights into the development of talented young professionals within MLS and the North American soccer ecosystem in general.

Through the lens of Complex Adaptive Systems (CAS), the third and final study (Chapter 6) aimed to [1] quantify the seasonal physical loading of an MLS homegrown player (age = 18 y; stature = 1.73 m; body mass = 68.7 kg; position = fullback) undergoing the youth-to-senior transition and [2] explore MLS sport scientists’ perspectives on the working dynamics and practices employed within their club to support player development during the youth-to-senior transition. A mixed methods single case study design was adopted, combining both club and national federation external loading data from global positioning systems (GPS) with semi-structured interviews conducted with sport science practitioners from the player’s MLS organisation. Descriptive statistics were used to analyse the quantitative GPS data, while hierarchical content analysis was employed to create meaningful categories from the qualitative interview data. This study’s findings underscore the need for a holistic, system-wide approach to the youth-to-senior transition in MLS, revealing how transitioning between club and national team (NT) settings creates complex developmental demands, variable physical loading, and organisational challenges that require adaptive, collaborative strategies to support homegrown player progression.

In summary, the findings from this thesis demonstrate that player development during the youth-to-senior transition is a unique, non-linear process in MLS. Further, it is shaped by the interdependence of club practitioners, different training environments, and the organizational structures established over recent decades. Accordingly, several avenues for future research are warranted, such as comparative mixed methods designs and longitudinal studies that track transitioning players across multiple seasons. Improving transition experiences and outcomes in MLS clubs will continue to rely on more strategic multidisciplinary coordination, staff alignment, and appropriate levels of responsiveness to young, developing players' needs.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Career transitions; Player development; Soccer
Subjects:	R Medicine > RC Internal medicine > RC1200 Sports Medicine
Divisions:	Sport and Exercise Sciences
Date of acceptance:	8 October 2025
Date of first compliant Open Access:	29 October 2025
Date Deposited:	29 Oct 2025 13:41
Last Modified:	29 Oct 2025 13:41
DOI or ID number:	10.24377/LJMU.t.00027326
Supervisors:	Littlewood, M, Roberts, S and Enright, K
URI:	https://researchonline.ljmu.ac.uk/id/eprint/27326

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