Thirlwell is back in training following a calf injury and the midfielder will be in contention to play at Ashton Gate.
Fellow midfielder Marc Bridge-Wilkinson continues to be troubled by a back problem which kept him out of Saturday's defeat to Exeter and he will not feature.
Peter Murphy returned to the side on Saturday in place of Richard Keogh (ankle) and is set to continue at the heart of United's defence alongside Danny Livesey.
Teenage defender Simon Lakeland is a long-term absentee with a knee ligament injury as Abbott looks to cause an upset against the Championship side.
