Injuries, Rotation and the Value of Subs
How much has squad depth contributed to success or failure in the Premier League?
In an attempt to break out of the doom spiral of following Liverpool in 2025/26, I opened a thread where anyone could ask football questions which I would attempt to answer (here, feel free to add to it). This query, from Butty, is essentially a three-parter:
“I’d be interested to understand how much squad depth contributes across the league. E.g. how many results were positively changed by substitutes or deputies. Maybe even going further, looking into if rotation reduces injuries or significantly improves performances of key players compared to previous seasons.”
Quantifying the impact of any of this is not easy. There are, however, some pertinent numbers for Liverpool which tell a tale about the problems they have had to endure this season.
We’ll begin with injuries. Leaving aside the construction of the squad, fitness issues ultimately shape what a manager can realistically change from week-to-week or in-game.
Arne Slot delivered a positive impact in this regard last season (as you can read in detail via the link below). Premier Injuries measure time-loss injuries, which are “any injury that results in a player missing at least one competitive fixture”. Liverpool suffered 4.3 per 1,000 minutes played in 2024/25 after being at 6.7 in Jürgen Klopp’s final campaign.
This improvement combined with Arsenal and Manchester City seeing their figures rise to 6.9 and 6.5 respectively last term likely helped the Reds win their second league title in six years.
Liverpool are at 7.9 this season.
That’s my calculation; it may be different with Premier Injuries, who provide their figures in an end of season summary rather than throughout the campaign. Their number shouldn’t be wildly different, with the Reds having collected (by my count) 34 time-loss injuries across 48 matches (4,320 minutes).
Despite losing players more frequently from what most would consider a weaker squad, Slot has been making fewer changes to his starting XI.
Rotation is not easy to assess across the Premier League, as clubs with European commitments play far more often. Manchester United will contest 40 games in 2025/26 whereas Liverpool will finish with somewhere between 57 and 60 on their ledger. Probably 57.
Managers also frequently make more changes for domestic cup games, especially if facing lower league opposition. The fairest method for comparing clubs is to look at the number of line-up amendments they make from one league game to the next.
The figures for Liverpool are a touch misleading. Slot averaged 1.9 changes per league match before the title was won last term, then raised that figure by giving some of his lesser lights a run-out.
Either way, these numbers suggest that rotation alone has no correlation with success. Brentford have improved after making the joint-third most changes per game; Newcastle and Wolves are lower in the table despite making even more. Nottingham Forest have maintained the most stable line-up in 2025/26 despite having four ‘permanent’ managers who could collectively be responsible for relegation.
While Slot is making essentially as many line-up changes between league games this season as he did in his rookie year, the numbers have shifted more notably for substitutes. That’s true for the volume of them, their average time on the pitch and the tangible output they have delivered in goals or assists.
