Wayne Rooney now appears overweight and faces a battle to prove he has a future at Manchester United, according to former Red Devils defender Paul Parker.
United captain Rooney, 30, started both the Community Shield and Premier League opener, with Jose Mourinho using the England international in a position behind striker Zlatan Ibrahimovic.
However, there have been concerns about his form for some time and he could find his place under threat from record signing Paul Pogba, who is now available after suspension, and Henrikh Mkhitaryan, who has so far been utilised from the bench.
"This is a defining season for Rooney," Parker, who played for Sir Alex Ferguson's United side from 1991 to 1996, told 888.com. "It's no longer about him breaking records but finishing his career at Manchester United. He needs to show his worth and that he deserves to be in the team and not just because of marketing.
"As much as people appreciate what he's done over the years and how many goals he's scored, football is about now and being judged on now. If someone had only heard of Wayne Rooney but seen him now they'd think, 'Who is this fella? He's overweight and slow.'"
On France international Pogba, who can play in a number of midfield roles, he said: "If he plays behind Ibrahimovic that puts Wayne Rooney in doubt and Rooney has to play -- not that he deserves a place, but they have to play him, so it's a difficult situation."
He added: "Pogba can get forward, and score goals, and pass the ball but in a high-tempo game, he won't be very good in a deep role. We saw that in the Euros where he looked lost for long periods of games when France didn't have the ball. So when United don't have the ball what's he going to be like?"
Parker also expressed concern about the state of United's squad, saying they still need a forward, centre-back and midfielder to compete at the top of the Premier League.
Sources have told ESPN FC that Mourinho is working on a deal for Southampton defender Jose Fonte but that United need to sell before they can buy.
"Would you say United can even finish top four after what we saw in the Bournemouth game? I'd have to say not really," Parker said. "Liverpool look good and Arsenal will improve. Tottenham and Chelsea are hard to break down and will be in there.
"So United have some work to do between now and the end of August to bring in at least three players to guarantee a Champions League spot and maybe win the league."
Parker criticised Mourinho's handling of former Germany captain Bastian Schweinsteiger, who has reportedly been sent to train with the reserves after being told he has no future at Old Trafford.
The former England international said Mourinho demands that his players "love him" and added: "If you work with someone, you may not like him but if he's doing a good job for you then you stick with him. With Mourinho, it doesn't work that way and therein lies the problem. That's why Schweinsteiger has been pushed away.
"There is no way Sir Alex would have handled the Schweinsteiger affair like Mourinho has done. He would be told he can leave but would have treated him with respect and still involved him in first team training as long as he had the right professional attitude.
"Mourinho never gave Schweinsteiger the opportunity to be professional about the situation."
Parker said there is a concern that Mourinho, who was dismissed as Chelsea boss in December after winning the title the previous season, is also creating problems.
"For Mourinho to be at the sharp end of Manchester United, that's a concern for me because he is saying that he has changed, but he said that at the start of his second spell at Chelsea," he said. "We saw what happened 12 months later [sic]."