Midfielder Thirlwell has missed the last two games due to a calf strain and defender Simek has been sidelined for four matches with a thigh problem.
Striker Danny Cadamarteri has undergone surgery to tidy up his knee joint and midfielder Dave Symington will play no part in the final game due to a knee problem.
Defender Chris Chantler (ankle) remains sidelined, but winger Matty Robson (back) returned to the starting line-up last week and lasted the full 90 minutes.
French forward Mathieu Manset is hoping to make his first start for the club as the Cumbrians chase their eighth home league win of the season.
- Sports & Recreation
- Danny Cadamarteri
- Matty Robson