Zlatan Ibrahimovic has been warned not to rush his Manchester United return by surgeon Freddie Fu Ho-keung, who operated on his knee in May.
Ibrahimovic has not played since suffering a career-threatening knee ligament injury in United's Europa League quarter-final second leg match against Anderlecht at Old Trafford in April.
"He (Zlatan) is very strong but soccer is still a combative sport. As a doctor, of course I want to see him return as slow as possible, only when he is fully fit for the game," Fu told the South China Morning Post.
"There have been many cases of a player returning prematurely with bad consequences."
United manager Jose Mourinho is keen on leaving the 35-year-old striker out of first-team plans until January though he included him in the squad for the Champions League group stage which runs from September to December.
"I have no worry about his injury as it always takes time to fully recover," Fu added.
"In fact the EPL (Premier League) has just started and I am sure Manchester United would not need the player urgently for any crucial game either in the league or European competitions."
Ibrahimovic finished as the club's top scorer last season with 28 goals in 46 appearances.
Morata's hamstring injury could keep him out for six weeks
Spain and Chelsea striker Alvaro Morata's hamstring problem could leave him sidelined for several weeks after tests with the national team revealed he has a grade two tear.
Morata had an MRI scan on Sunday after limping off during Chelsea's 1-0 Premier League home defeat by ManchesterCity on Saturday. According to British media reports on Tuesday, the injury could keep him out for at least six weeks.
Spain manager Julian Lopetegui on Monday called up 36-year-old Athletic Bilbao striker Aritz Aduriz to replace Morata, with the Blues forward missing Spain's final World Cup 2018 qualifying matches against Albania and Israel.
Spain are also missing injured duo Andres Iniesta of Barcelona and Dani Carvajal of Real Madrid, replaced by Las Palmas' Jonathan Viera and Real Sociedad's Avaro Odriozola, as the Group G leaders bid to earn a place at the finals in Russia.
The Spaniards are three points clear of second-placed Italy with just the two rounds of matches remaining.
Chelsea signed Morata from Real Madrid in the close season and the striker has flourished at StamfordBridge, with seven goals in nine appearances for Antonio Conte's champions.
If Morata's worst fears are confirmed he will miss both of Chelsea's Champions League group stage matches against AS Roma and several Premier League games, including the home clash with Manchester United on November 5.