The defender has completed the six-match ban he received for his part in the brawl at Bradford in March which also resulted in him being stripped of the captaincy.
Mills was an unused substitute for the shock 3-0 defeat by Hereford last week has since proved his fitness with a run-out for the reserves.
Goalkeeper Scott Shearer (knee) and right-back David Hunt (broken foot) also played for the second string to build up their fitness.
Midfielder Hope Akpan is still suspended for his red card against AFC Wimbledon last month.
Crawley know a victory would guarantee automatic promotion to League One ahead of Torquay and Southend.
A handful of youth-team players are pushing for inclusion as Accrington boss Paul Cook prepares to look towards the future.
Striker Marcus Carver made his debut from the bench in last weekend's defeat at Bristol Rovers and is ready for further action, while midfielder Adam Stockdale is eying his own Stanley bow having narrowly missed out on the matchday squad at the Memorial Stadium.
Both players penned their first professional deals at the Crown Ground this week, alongside Ryan Hopper, who will look to add to his four appearances in midfield under Cook's stewardship.
Ian Craney is no longer an option in the engine room after he failed to agree a new deal, bringing his third stint with the Reds to a close.
Will Hatfield is expected to remain on the sidelines with a hamstring injury alongside defenders Dean Winnard (ankle), Danny Coid (knee) and Sean Hessey (hamstring).