Dallas defensive end Randy Gregory is active for the first time this season against Detroit on Monday night after serving a 14-game suspension for violating the NFL's substance abuse policy.
Gregory was originally suspended four games before a 10-game ban was added during the season for another violation by the second-year player who slid to the second round of the 2015 draft in part because of concerns over marijuana use.
The Lions are without cornerback Darius Slay because of a hamstring injury that also sidelined him for two games in November. Running back Theo Riddick is out for the third straight game because of a wrist injury.
Detroit center Travis Swanson misses his third straight game with a concussion.
Starting Dallas defensive end Tyrone Crawford is out for the first time this season with shoulder and hamstring injuries.