Celtic will not be expelled from the Europa League, even if play-off opponents Sion are reinstated in the competition.
Uefa will contact the clubs in Group I next week to outline provisional plans should the Swiss side be successful in their appeal against expulsion.
But the removal of the Glasgow side will not be considered as an option.
A five-team group, with Sion added to the line-up, appears to be the more likely outcome.
The Swiss Cup champions defeated Celtic 3-1 on aggregate when they met in August but were judged by Uefa to have fielded ineligible players.
This is obviously detrimental to the smooth running of the competition and also has a negative impact on the other clubs participating in the group, for whom FC Sion has no apparent respectUefa statement
Celtic took Sion's place in Group I and have already played games against Atletico Madrid and Udinese.
The Swiss side were expelled from the tournament and an initial appeal against the decision was rejected.
In a statement on its website, Uefa has outlined its desire for accelerated action in the case, via the Court of Arbitration for Sport.
"It seems that FC Sion has repeatedly attempted to obstruct justice and, as quoted by the CAS decision of yesterday, has engaged in a "clear abuse of procedures" to delay or postpone a decision on the merits of the case," the statement said.
"This is obviously detrimental to the smooth running of the competition and also has a negative impact on the other clubs participating in the group, for whom FC Sion has no apparent respect."