Both Manchester City manager Manuel Pellegrini and Manchester United's David Moyes have first-team injury doubts ahead of Sunday's derby clash.
The two clubs return to Premier League action at the Etihad Stadium after respective wins in their opening Champions League matches but have a few team selection issues to resolve.
City midfielder David Silva is fit and has returned to first-team training after a hamstring problem but there are suggestions from Carrington that Pellegrini may be tempted to start with Samir Nasri after his performance in Tuesday's win over Viktoria Plzen.
Gael Clichy is still struggling with a knock and faces late fitness tests on Friday, with Aleksandar Kolarov likely to start at left-back, but Micah Richards should be back in the squad.
As for the visitors, Danny Welbeck is a doubt with United's medical staff struggling to fix the fluid in his knee. The England forward missed training earlier in the week and, although he is being eased back into things, still has not taken part in a full-contact session.
Instead, the 22-year-old striker has stuck to light jogging and similar personal exercise and is therefore unlikely to start - but he could make the matchday squad on Sunday.
Moyes also has some concerns in defence. The former Everton boss is reluctant to to play Rio Ferdinand three games in a row, with worries about the 34-year-old's general wear and tear ahead of a long season, but other injuries mean that he may well have to do so.
Phil Jones is suffering from an ankle injury and there is uncertainty over the extent of Rafael's hamstring problem, with the latter set to be monitored right up until the end of training on Saturday.