A win at Hatrick Park against Navan will guarantee Rainey on Saturday a home semi-final in the Ulster Bank Divison 2A/2B play-offs.
Old Crescent have already secured the Division 2B title and promotion, Rainey are eight points clear of third placed Barnhall.
Prop Tommy O’Hagan is set to make his Ulster senior debut from the bench tonight at Edinburgh but could be available for the Old Boys.
Jody McMurray could move to centre while Josh McIlroy may be deployed in the backrow as he was against Wanderers to give Rainey more pace around the park.
There is an Ulster derby at Deramore between Belfast Harlequins and City of Derry but both sides’ fates have already been decided.
Derry have been relegated and Quins will have to navigate the playoffs to avoid joining them in Division 2C next season. Dungannon host Sunday’s Well.