Carsley has stepped up from the Under-21s to take over the reins at senior level, following Gareth Southgate's departure in the wake of the Euro 2024 final defeat to Spain.
Mainoo played in that game in Berlin and had a very influential tournament after breaking into the set-up on the back of his outstanding work for United last season.
Maguire had been a key figure at the heart of the Three Lions' defence under Southgate but was forced to miss the finals due to injury.