Jose Mourinho has been blamed for Romelu Lukaku's poor Manchester United form.
The Belgian striker started the Premier League season brightly with four early goals - but he has not scored for his club since September and was dropped to the bench for the recent games against Everton and Manchester City.
Former Chelsea striker Tony Cascarino says his sluggish performances are down to not getting enough recovery time after the summer's World Cup.
And he points to Stamford Bridge chief Maurizio Sarri's handling of Lukaku's Belgium team-mate Eden Hazard as the kind of strategy United manager Mourinho should have adopted with his player.
“I don’t think I’ve ever seen Hazard work so hard in a game.
“Fast-forward to the start of the season and he was eased into the Chelsea line-up by Maurizio Sarri, playing 14 minutes in their first game against Huddersfield Town and then 29 minutes against Arsenal.
“Sarri realised that Hazard needed a rest so he took him out of the firing line.
“The same cannot be said for Jose’s management of Lukaku."
Cascarino believes Lukaku, 25, is worn out and that United's position - they sit eighth, 12 points off leaders City - is, in part, a consequence of the centre-forward's struggles.
“He came on as a substitute in their opening match against Leicester City but then played every minute of their next 12 matches, despite his form wavering and him looking short of fitness," added Cascarino, who played for Chelsea between 1992 and 1994.
“Modern-day players do everything they can to be as fit as possible and, because they work so hard during the week and in matches, injuries become inevitable.
“Someone has to step in and protect players when they are with their clubs, the manager or the medical team.
“It is no surprise that the three unbeaten teams this season are ones at which the managers are juggling their squads.
“Sarri has used Hazard wisely, Pep Guardiola has rotated his Manchester City midfield to keep them fresh and, at Liverpool, Virgil van Dijk and Georginio Wijnaldum have been outstanding.”