Explained: Why Cole Palmer isn't playing against Arsenal and when he could return for Chelsea

The England international completed 90 minutes on Saturday as the Blues lost 1-0 to City in the semi-finals of the FA Cup at Wembley. However, he is not on Chelsea's bench for Tuesday night's trip to the Emirates - let alone in the starting lineup. So why is he not featuring in this London derby?

On Monday, Chelsea manager Mauricio Pochettino revealed the 21-year-old had been suffering from illness since that match. That has kept him out of team training, with the Argentine admitting he would make a late call over the former City youngster. Now, it has become clear Chelsea's top scorer, who has bagged 20 league goals this season, has not recovered in time for the encounter.

On Monday, the former Tottenham boss said on Palmer: "We need to assess tomorrow (Tuesday) morning but today I don’t believe he can be involved. We need to assess tomorrow and then decide. Even if he is feeling better tomorrow, maybe he is not in a condition to play. We hope he recovers from this situation and can be involved again as soon as possible. With or without Cole we always believe we can win. The most important thing is the team and the collective. He is an important part of the team and is doing fantastic for us, but we are Chelsea and we have plenty of players that can perform and do the job."

In a season that promised so much but delivered so little, Palmer has been one of the few positives at Stamford Bridge. The £42.5 million ($53m) recruit from City has scored 23 goals and bagged 13 assists in all competitions and without him they would be nowhere near trying to qualify for Europe. In truth, they would have been closer to the relegation zone than the top seven. Therefore, his presence may be sorely missed against Premier League title hopefuls Arsenal.

Chelsea have named a starting XI with an average age of under-24 for the seventh time in the Premier League this season, with only Leeds United in 1999-2000 having more in a single campaign (10).

Chelsea, who sit ninth in the Premier League, will hope Palmer will be fit and raring to go for their next clash on Saturday night - an away trip to Champions league hopefuls Aston Villa at Villa Park.