West Ham manager Slaven Bilic has admitted that summer signing Marko Arnautovic has made a "slow start" to his Hammers career.
The Austrian winger arrived at the London Stadium for £25m from Stoke City, but has so far struggled to make an impact.
Arnautovic served a three-game ban through suspension having been sent off against Southampton in August, and missed last month's win over Swansea with an illness.
And Bilic has stressed that his difficult start is down to his own "mistake".
"Yes, he has made a slow start," the Croatian coach said, quoted by Sky Sports. "But that is because he got suspended for three games and then he missed the last game, because of the flu he got.
"His slow start is because of his mistake."
Arnautovic was taken off in Saturday's 1-1 draw against Burnley after striker Andy Carroll was sent off.
"This [substitution] was just tactical," Bilic said. "He didn't go out because of a bad performance, he was taken off because my staff and I decided we needed an extra man in midfield. I think it was a good decision."
Bilic could be left with some selection dilemmas in attacking areas in the coming weeks, with both Andre Ayew and Diafra Sakho unused substitutes at Burnley and Manuel Lanzini returning from injury.
"It is difficult but it happens to most clubs in the moment they have all their players," Bilic added.
"Not every team is in the position of Crystal Palace, all the strikers injured or out. You have a squad with numbers, because very rarely are you in a position to choose from your whole squad."