West Ham's proposed deal to sign Samir Nasri is in doubt because of concerns over the player's fitness, Sky Sports News understands.
The experienced France forward underwent a medical with the club on Monday, but they are worried about how long it will take him to reach the required fitness levels to play in the Premier League after 18 months out.
The Hammers' initial proposal of a six-month deal with another year's option, with wages thought to be around £80,000-per-week, could therefore be revised.
Nasri was banned from football for breaching World Anti-Doping Agency (WADA) rules in 2016 after he visited an intravenous treatment centre in Los Angeles, but he can play again from January 1.
West Ham manager Manuel Pellegrini wants to sign Nasri, who he deployed to great effect during their time together at Manchester City, and he has been free to train with the squad since the beginning of November.