Lampard backs under-fire Mourinho
Mourinho is under increasing pressure after seeing United collect just 10 points from their opening seven Premier League games.
The Portuguese tactician endured a difficult week in which his side were knocked out of the EFL Cup by Lampard's Derby County before losing to West Ham.
Lampard, who played under Mourinho at Chelsea, said he felt for his former boss.
"Everyone knows my feelings for Jose Mourinho as a manager," Lampard said. "It is a tough moment. It is a moment that we will all have, that I will have at times, that every manager has.
"I have heard all his interviews lately. He is a big boy. He will get about doing his job. Of course I feel for him. They are not winning games and they want to be - it is Manchester United.
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"In terms of players, it can be difficult. You need buy in from your players and you need sometimes the right message to be coming out. I thought that as a player and I think it even more as a manager.
"And you need complete work rate on the pitch. I am not talking about individuals here, I am saying that is what you need."
United get a chance to return to winning ways when they host Valencia in the Champions League on Tuesday.