Thomas Tuchel has confirmed Christian Pulisic has tested positive for Covid-19 with N'Golo Kante and Hakim Ziyech to undergo late fitness tests ahead of the trip to Arsenal.
Pulisic was absent from Wednesday's open training session at Stamford Bridge with the Chelsea manager revealing the USA international is now in isolation after returning a positive test.
Kante meanwhile missed the season opener against Crystal Palace with an ankle injury picked up in the Uefa Super Cup victory over Villarreal.
Ziyech suffered a dislocated shoulder during pre-season but both players have returned to training and are pushing for returns on Sunday.
'Christian has unfortunately had a positive test and needs to follow the protocols,' Tuchel told a press conference on Friday.
'He's not been training and is not available for the game.
'Hakim and N'Golo both trained yesterday and had absolutely no problems. So we need to have more physical intense session tomorrow and decide tomorrow.
'Right now, it seems very positive that both can be in the squad for Sunday.'
Romelu Lukaku meanwhile began training with his new team on Tuesday with the Belgium international set to have some role to play against the Gunners.
'We have one more training session to go but the week was a heavy load,' Tuchel added.
'He was with the group with the late starters, so it was an overload week so far.
'Today was low intensity and tomorrow we will have an important session before the match.
'We hope he will be on the pitch on Sunday and it looks likely.'