While it's believed Saka is making every effort to get back on the field at the earliest opportunity, the complaint - thought to be Achilles tendinopathy - is sensitive and if his rehabilitation is accelerated, there is danger Arsenal could find themselves without him for the rest of the season.
He hasn't yet been ruled out of involvement this weekend, but would require improvement and a return to training in the next few days to have any prospect of being selected.
Mikel Arteta said on Tuesday: "It's something that he was carrying for a while. It was an Achilles issue. It's progression but hopefully it's going to be a matter of days and not weeks. But he has to see when the load is more how he responds to that kind of progression."
Saka's replacement, Noni Madueke, was similarly withdrawn with a knee problem in the second half against Sporting CP, though there was tentative confidence he escaped injury.
Meanwhile, sources close to left-back Riccardo Calafiori have suggested he stands a chance of featuring against City after recovering from his recent injury.
Calafiori was in high spirits at the Emirates last night and was spotted dancing near the players' lounge following his side's 0-0 draw with Sporting CP, having picked up the problem during the first leg.
Jurrien Timber was also present and last Saturday, following the 2-1 home defeat to Bournemouth, he confirmed he was "recovering" as he walked past the mixed zone.
Timber declined to shed any light on when he might return from the groin injury he sustained in the 2-0 home victory over Everton on March 14.
When quizzed on whether he could be available to face City, he responded evasively: "I can't say. But we'll see."
Captain Martin Odegaard confirmed in his Arsenal programme notes that he tweaked his knee during last week's 1-0 win over Sporting in Lisbon. The Norwegian made it clear he's striving to return as quickly as possible.