McManaman, who has never won England's top prize, was speaking on BT Sport's Football Tonight show.
“I think they are miles away, £150 million away from winning the title," he said.
"I have been disappointed with the way they have played. I think the fact that they played so well against Liverpool and Tottenham has rescued them.
"I expected them to play much better and be closer, as in they have never ever been anywhere near challenging for the title this year.
"They have got a little bit closer at the end of the season as other teams have tailed off.
"So I expected them to be closer playing a better standard of football. To have no European football this year has helped them considerably.”
The Red Devils have been heavily linked with moves for Borussia Dortmund duo Mats Hummels and Ilkay Gundogan this summer.
The German internationals will cost a minimum of £50 million leaving United a sizeable transfer kitty to play with if they are to invest as significantly as they did during Louis van Gaal's first window.
This kitty would become almost a bottom-less pit of cash if Angel di Maria or David de Gea - both linked with moves away - were to be sold, although that does still seem very unlikely indeed.
But the Old Trafford club could attract their own Galacticos this summer with potential moves for superstars Paul Pogba and Gareth Bale, something that would surely go down well with the supporters.
Who do you think Manchester United should sign this summer? Let us know below!