Louis van Gaal has "wasted money" at Manchester United and Anthony Martial is shouldering too much responsibility, according to Tony Cottee.
United went a sixth game without victory as Norwich City inflicted their first home defeat of the season with a deserved 2-1 victory at Old Trafford on Saturday.
And, with the defeat heaping further doubt on Van Gaal's future, Cottee believes a time will come when United will be left with no choice other than to part company with the Dutchman.
"A decision over the manager will come if they don't get the results, given the run of form that they have been in," Cottee told Soccer Saturday.
"Manchester United are normally pretty loyal, they are not a panic club, but there comes a time where performances aren't good enough.
"They have two big football matches coming up against Stoke and Chelsea so I don't suspect they will do anything between now and the New Year but things are just not good enough for Manchester United."
United sit fifth in the Premier League, nine points adrift of leaders Leicester City following Saturday's loss.
Live Ford Football Special
Van Gaal has splashed £250m during his 18-month spell in the Old Trafford hot seat, yet consistency of results have not arrived despite his significant outlay.
And, asked whether the Dutchman should be handed more money to overcome United's toils, Cottee added: "A lot of the money they have spent has been wasted, I wouldn't give Van Gaal anymore money in the January transfer window.
"Players are playing below par and there is too much responsibility on [Anthony] Martial's shoulders.
"There were countless times where the ball went flashing across the face of goal in both halves and there wasn't a Javier Hernandez or James Wilson there for the simple tap-ins - there was no one in the box.
"This is a huge problem for them and I do fear for Manchester United, I don't know where they are going as a football club.
A decision over the manager will come if they don’t get the results, given the run of form that they have been in.
"United had just two shots on target, which is incredible at Old Trafford. That wouldn't happen in the past. You are not going to win football matches with two shots on target and it is not good enough for Manchester United football club.
"They are in trouble. Even when United got back to a goal behind, they pushed forward but the final ball, the final pass, the final cross was awful.
"By the end the crowd were getting a bit agitated and it's not good enough."