Bush was limited in Detroit's win over the Miami Dolphins on Sunday due to the injury. The running back has sat out two games this season, and Caldwell said Monday that he tweaked his ankle during the game.
Though Bush's injury is not serious, the Lions may hold him out just to ensure it fully heals. The team took a similar strategy with wide receiver Calvin Johnson's lingering ankle injury earlier this year.
Bush had four carries for 20 yards and one reception for five yards against the Dolphins. He has just 43 rushing yards on 14 carries in his last three games.
A 1,000-yard rusher a season ago, Bush has just 191 yards in seven games this season, and his 3.6-yard-per-carry average is his lowest since his rookie season in 2006 with the New Orleans Saints.
With Bush still injured, the Lions will continue to rely on power back Joique Bell and versatile second-year pro Theo Riddick.
Detroit's running game has struggled this season. The Lions are 31st in the league with only 77.8 yards per game.
The team improved to 7-2 with its win over the Dolphins. Detroit will meet the 8-1 Arizona Cardinals on Sunday.
- Phil Watson