Thursday’s game is the second in succession the 29-year-old England forward has not featured in a matchday squad, after he was omitted from Chelsea’s Premier League opener with Manchester City.
Defenders Ben Chilwell, Wesley Fofana and Tosin Adarabioyo were also not included on Chelsea’s A-list submitted to Uefa for Thursday’s match at Stamford Bridge (20:00 BST), with the second leg in Switzerland on 29 August.
Should Chelsea progress they could name Sterling in their squad for the Conference League group stage.
Sterling’s representatives said in a statement before Sunday’s defeat by City they wanted “clarity” over the player’s future at the club.
Chelsea have spent about £185m on 11 signings this summer, leaving manager Enzo Maresca with a squad of more than 40 senior players.
Maresca said after the City game he “wants” Sterling at Chelsea, but acknowledged “there is not enough space” for all his players to feature in matches.
Sterling has made 81 appearances for Chelsea since he joined from Manchester City for £50m in July 2022.