Bayern Munich legend Oliver Khan has backed the club's sale of Bastian Schweinsteiger but has told the Germany captain he must adapt to the Premier League quickly.
Schweinsteiger, 31, moved to Old Trafford last month much to disappointment from Bayern fans - a move that Khan agreed was the right call, reports BT Sport.
"A club cannot make allowances for what a player has achieved for them, but they are responsible for looking at what he is currently doing for them," Kahn told Kicker magazine.
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"I certainly don't think Schweinsteiger would have been suited to being a back-up player."
"With that in mind, this decision is understandable."
Schweinsteiger's place in Pep Guardiola's side had come under threat in recent seasons with new, younger options coming in and his recurring injury and fitness problems.
Thiago Alcantara, David Alaba and new signing Joshua Kimmich are all younger than Schweinsteiger, while Xabi Alonso and captain Philipp Lahm have both impressed in the role. Arturo Vidal is another recent big-money signing who is expected to fill in that position.
But although Khan thinks the transfer was the right move, he has a warning for United's new man.
"Bayern's style of play was suited to him, but he's going to have to adapt to an extremely high tempo at Manchester United," said Kahn.
"He could run into problems relatively quickly if he does not get back to a top physical condition."
Schweinsteiger made his Man United debut from the bench at home to Tottenham on Saturday after being deemed not fit enough to start by Red Devils boss Louis van Gaal. United ran out 1-0 winners thanks to a Kyle Walker own goal.