Paul Pogba and defenders Eric Bailly, Chris Smalling and Phil Jones all trained on the eve of Manchester United's Europa League semi-final first leg at Celta Vigo on Thursday.
England pair Smalling and Jones have been out since mid-March, while fellow centre-back Bailly limped off in the 61st minute of United's 1-1 draw with Swansea City on Sunday.
With left-back Luke Shaw sustaining a foot injury in the same game, United were facing a defensive injury crisis, but manager Jose Mourinho may now have more options at his disposal than anticipated.
Record signing Pogba's return to the training pitch at United's Carrington base west of Manchester will also be welcome after he missed their last two games with muscle fatigue.
Mourinho has been critical of Smalling and Jones for not being prepared to play through the pain barrier.
It is unclear whether either they or Bailly will be fit to start in Vigo on Thursday.
Defender Marcos Rojo and striker Zlatan Ibrahimovic are out after both sustained knee ligament damage during United's quarter-final success against Anderlecht last month.
Midfielder Juan Mata could make his first appearance since groin injury, while Marouane Fellaini is available despite currently serving a three-game domestic suspension.