The Portuguese boss says that depleted numbers in training was the decision to bring the World Cup winner back into the fold
Manchester United manager Jose Mourinho has referred to the decision to reintroduce Bastian Schweinsteiger into first team training as one "that can be positive for the group".
Speaking ahead of United's clash with Turkish side Fenerbahçe S.K. on Thursday night, Mourinho did however leave little doubt over the German World Cup winner's place within the squad.
"We made the decision last Thursday, we informed him last Friday so he joined the team last Monday," he said.
"It's a decision based on the fact that we're in a period where it's really difficult to train with everybody together.
"In this moment, the next day after we play, the players who played train in a different recovery session so the group becomes 13, 14, and with injuries sometimes 10, 11.
The 32-year-old also confirmed in a statement at the start of the season that United would be his last club in Europe before he moves on with his career or retires. Mourinho dispelled any idea that the former Bayern Munich midfielder would become a regular member of the squad.
"He'll be in much better condition in case his future decision is to leave the club. If he stays with us and becomes one more option - and in this moment we have no problems in midfield - but if we do one day then he will be one more option.
"It's a decision that can be positive for the group, so it's good for us and for him."
Manchester United have struggled to find form in recent weeks with only two wins in their last six games in all competitions.
Their last win in the league came on September 24 when they beat champions Leicester City 4-1 at Old Trafford.