Claude Davis has failed to recover from a knee injury in time for Crawley's FA Cup third round tie with Reading at Broadfield Stadium.
Davis missed the 3-0 victory over Colchester United last weekend and had a scan on the problem on Wednesday but has failed to recover in time.
It means Joe Walsh continues alongside Mark Connolly in the centre of defence as boss Richie Barker names an unchanged side.
The only difference is the inclusion of new signing Lateef Eldorf-Alliyu on the bench in place of Nicky Ajose, who has returned to Peterborough after his loan spell, and John Akinde for cup-tied Jonte Smith.
Reading make seven changes to the side which lost 3-1 at Tottenham last weekend with top scorer Pavel Pogrebnyak among those to drop out.
Crawley (4-4-2): P Jones; Hunt, Connolly, Walsh, Sadler; Adams, Akpan, Simpson, M Jones; Clarke, Alexander. Subs: Kuipers, Bulman, Cooper, Torres, Akinde, Eldorf-Alliyu.
Reading (4-5-2): Federici; Cummings, Pearce, Morrison, Harte; Robson-Kanu, Tabb, Karacan, McCleary, Hunt, Le Fondre. Subs: Taylor, Gunter, Shorey, Mariappa, Guthrie, Church, Ugwu.