Ulster coach Mark Anscombe expects Lions duo Rory Best and Tommy Bowe to make their competitive return against Benetton Treviso on 27 September.
Wing Bowe and hooker Best are being eased back to full fitness following the successful Lions tour of Australia.
Iain Henderson and Stuart Olding, who both played in Ireland's tour of North America, are likely to return for the game with Glasgow on 13 September.
Stephen Ferris is continuing his recovery from an ankle injury.
The Ireland flanker agreed a six-month extension to his Ulster deal in June, in an attempt to regain full fitness.
Anscombe said it was too early to put a date on a comeback for Ferris, and added it was "still a long way off".
Bowe missed the first Test against the Aussies after he broke his hand but made a remarkable recovery to play in the second Test.
Ulster start their Pro12 campaign against the Newport Gwent Dragons at Rodney Parade on Friday, 6 September.