The Red Devils were beaten 3-0 in the Premier League by Tottenham at home on Sunday.
Redknapp indicated that the team's lackluster play could be putting manager Erik ten Hag's position at risk.
Redknapp's comments came after a particularly disappointing game, suggesting that time may be running short for ten Hag to turn things around.
"It gets to a point where you almost feel sorry for the manager as well," said Redknapp post-game.
"He looks completely out of his depth, he looks like he's struggling to motivate his team. United and Ten Hag are going backwards.
"You can't complain any more. He's got his back four in place, he's got all the players at his disposal. There are no excuses.
"They are rock bottom right now. I just don't see where they can go from here. They're as bad as I've seen a United side. It's embarrassing. A club of this stature shouldn't be producing performances like that."