Slaven Bilic admits record signing Marko Arnautovic is having a "slow start" to his West Ham career.
Arnautovic arrived from Stoke in the summer for a fee worth up to £25million but the Austrian playmaker has yet to make much of a downpayment on that.
He was sent off in his second appearance for the club, for a dangerous elbow on Southampton's Jack Stephens, missed the next three games through suspension and sat out the win over Swansea with illness.
Saturday's trip to Burnley saw him restored to the starting XI but Andy Carroll's early red card saw Arnautovic sacrificed at half-time in a tactical switch as West Ham took a 1-1 draw.
Two months on from his debut, Bilic accepted Hammers fans have still to see the best of the former Werder Bremen forward.
"Yes, he has made a slow start but that is because he got suspended for three games and then he missed the last game because of the the flu he got," said the Croatian.
"His slow start is because of his mistake. This (substitution) was just tactical: 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."
The encouraging second half display of his replacement, the more industrious Pedro Obiang, and the presence of fit-again Manuel Lanzini, could mean the squeeze is on for Arnautovic in the starting XI.
Andre Ayew and Diafra Sakho were both unused substitutes at Turf Moor, giving Bilic decisions to make in the coming weeks,
"It is difficult but it happens to most clubs in the moment they have all their players," he said.
"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."
Burnley went behind to Michail Antonio's 19th-minute effort, gifted to the visitors after errors from Ben Mee and Nick Pope, and only equalised with five minutes left on the clock.
Chris Wood was the man to get the job done, netting for the fourth time since his £15million move from Leeds.
"As a striker you've just got to keep going because there's always going to be another chance," he told the club's official website.
"It was a bit of a frustrating one and against 10 men we could perhaps have done a bit more, but I think if the goal had come earlier in the half we would have gone on to win it.
"We have to keep working and finding ways of breaking people down and we will be onto a winner. Six unbeaten is a fantastic record, which is something we'll look to build on next weekend."