Tansey this week underwent an operation on a niggling groin problem which has kept him out of the last couple of matches.
Fellow midfielder Shroot is also facing a spell on the sidelines after he was stretchered off with an ankle injury against Hartlepool on Monday.
Anthony Grant came on for Shroot and could start at Fratton Park, although Gavin Mahon provides another option if he is fit.
Left-back Miguel Comminges returns after a one-match ban but fellow defenders Lee Hills (hamstring) and Jon Ashton (Achilles) are out.
Rookie defender Alex Smith will be hoping to make his debut following his recent loan switch from Fulham.