Substitutions have transformed football - but winning teams still rely on youth and consistency

As football adapts to an era of five substitutes, tactical flexibility and ever-increasing physical demands, new research from the University of Wolverhampton shows that while substitutions have reshaped the game, the most successful teams continue to rely on consistent starting line-ups and younger players.

The study, published in the International Journal of Sports Science & Coaching, analysed English top-flight football across six decades, tracking how substitutions, player age and squad use have evolved between the 1973–74 and 2023–24 seasons.

A game transformed by substitutions

The research confirms that substitutions have increased significantly over time, driven by rule changes that have expanded the number of players managers can bring into a match; from just one substitute in the 1970s to up to five in the modern game.

These changes have made substitutions a central part of modern football strategy, allowing teams to adapt to match situations, manage workloads and make tactical adjustments throughout a game.

The study also identifies a shift in how substitutions are used, with replacements more likely to involve defenders than attackers - suggesting managers are using substitutions proactively to influence matches rather than simply protect a lead.

But the best teams don’t rely on them as much

Despite this transformation, the research reveals a striking finding: the most successful teams, those finishing in the top six, consistently rely more on their first-choice players and use fewer substitutes overall.

This suggests that while substitutions are now a powerful tactical tool, success at the highest level still depends on maintaining a stable and cohesive starting line-up.

Youth remains a decisive factor

Alongside consistency, age emerges as a key differentiator between successful and less successful teams.

Across the decades studied, top teams consistently field younger players, with an average age of 25.8 compared to 26.9 for lower-ranked sides - a statistically significant difference.

The findings highlight the continued importance of youth development and investment in academy systems, with younger players appearing better suited to the demands of the modern, high-tempo game.

A balance between flexibility and stability

Lead researcher Professor Alan Nevill from the University of Wolverhampton said:

“Substitutions have become a fundamental part of modern football, giving coaches more options to change games as they unfold.

However, our findings show that the most successful teams still place great trust in their starting players and tend to make fewer changes. At the same time, they consistently select younger squads, which may reflect the physical and tactical demands of today’s game.”

Explaining today’s football

The research paints a picture of a sport that has evolved significantly over the past 50 years.

On one hand, managers now have unprecedented flexibility to intervene during matches, using substitutions to respond to opposition tactics and manage intensity.

On the other, the foundations of success remain rooted in:

• a consistent, well-drilled starting XI
• younger, high-potential players
• long-term squad cohesion

A modern paradox

Taken together, the findings reveal a defining paradox in contemporary football: while the game has become more flexible and dynamic due to increased substitutions, the most successful teams continue to prioritise stability and youth.

As major tournaments showcase the impact of players coming off the bench and late tactical changes, the research suggests that true success lies in balancing innovation with consistency.