Boss Jose Mourinho says striker Diego Costa could be ruled out for Chelsea's Premier League opener against Swansea City next week.
The Spaniard was expected to be in the starting line-up to face Arsenal on Sunday afternoon but was not even on the bench as Loic Remy started the game for the Blues.
The Frenchman struggled to make an impact and was replaced by Radamel Falcao in the second half.
The Colombian was more lively in the offensive department but lost all battles against the Arsenal defence.
"Two days ago he [Diego Costa] was ready to play," Mourinho told reporters.
"When I told you two days ago he was ready to play he was ready to play. He trained normally on Friday and yesterday at the end of the training session he said he was not feeling good.
"But Falcao will have had a bit more football, he will play against Fiorentina from the start. We have Remy too, so if we don't have Diego I am happy with the strikers I have.
"I expected the lack of sharpness, it's normal. Some players like Falcao started a week ago.
"The others have had two weeks and half of this week. The pitch was a disaster, so slow, the weather didn't help too but it was the same for both teams so no excuses. I know Arsenal also like a good, fast pitch.
"One team played counter-attack football well. One team played with initiative well but without the sharpness you need to be more aggressive with the ball. The team tactically tried everything."