By FOX Sports Staff
Rooney trudged off the pitch in the 71st minute of United's 2-2 draw at West Ham on Wednesday with his team trailing 2-1.
New summer signing Robin van Persie grabbed the equalising goal six minutes later to reinforce his new position as Sir Alex Ferguson's key man.
The Dutchman was also picked ahead of Rooney to start as United's lone striker in a crucial UEFA Champions League game against Real Madrid at Old Trafford earlier in the year.
And the sight of an unhappy Rooney being subbed on Wednesday when his team were in need of a goal has caused Shearer to ponder the former Evertonian's role with the English champions.
"Looking at it, things don't seem right," Shearer told the Sun.
"He has been left out of the team, shunted around [in different positions] and been subbed more than once.
"I would be wondering just where I stand.
"If he is not happy, he needs to move."
Since the England international's future at the club has come under the spotlight, Ligue 1 leaders Paris Saint-Germain have emerged as the favourites for Rooney's signature.
Given that Rooney is obviously no longer United's first choice striker, Shearer feels there is little option left but for the talented player to leave.
"It is obvious he is not the No. 1 there any more. Robin van Persie is the automatic choice up front," Shearer said.
"Wayne is not even certain of being on the teamsheet, as was proved against Real Madrid at Old Trafford.
"It was a decision I didn't agree with and must have made Wayne wonder where he stands at United right now.
"He is still England's main hope yet he wasn't good enough for Manchester United on their biggest night of the season for what were described as ‘tactical reasons'."
He added: "I have to ask myself if he had not scored for 10 games, like Robin van Persie recently, whether the manager would have persevered with him."
"I have always said that Rooney would be the best player on the pitch wherever he plays, bar in goal.
"Right now, that is being tested, too. He has gone from the main frontman, to the supporting role in behind Van Persie, to out wide and a deep-lying midfield role.
"You have to ask yourself whether this would happen to someone like Cristiano Ronaldo or Lionel Messi.
"People will say that he is not in their class.
"But three or four years ago he was being talked about in the same breath.
"He is 27 and these should be the best years of his career coming up but he is not at the level we all expected he would be.
"He has to sit down with his advisors in the summer and ask himself whether or not a move would be beneficial.
"He is already at a great club with a great manager but things just don't look rosy to me."
Rooney has found the back of the net 16 times for United this season so far.