Manchester United's return to the Champions League will test their squad depth after a busy summer of spending. Despite investing over £1bn since 2022, the highest net spend in the Premier League, their defence remains neglected. Only 19 per cent of that spending went on defenders, the third-lowest ratio among top clubs. This imbalance leaves their backline vulnerable as they face up to 67 games this season.

Last term, United played just 40 matches due to early cup exits and no European football, allowing manager Erik ten Hag to field a consistent XI. That consistency helped them finish third, but it won't be possible with midweek Champions League fixtures. Ten Hag has welcomed the challenge, noting players prefer more involvement, but the squad's lack of turnover is concerning.

Remarkably, the back four that started Ten Hag's first game in 2022—Luke Shaw, Lisandro Martinez, Harry Maguire, and Diogo Dalot—remains unchanged. Six of the same starters featured in Sunday's 2-2 draw with Everton, highlighting a retention rate of 54.5 per cent. While experience helps, the failure to strengthen key areas, especially defence, could cost them in Europe's top competition.