Suh and the Lions are waiting to hear about potential discipline from when Suh stepped on the calf and ankle of Green Bay Packers quarterback Aaron Rodgers twice during the fourth quarter of the Packers' 30-20 win over the Lions on Sunday.
A league source told ESPN's Chris Mortensen that Suh's history with safety issues could play a role in whether the NFL suspends the Lions star. Mortensen also reported that if the league doesn't suspend Suh, it could fine him heavily.
As for what he thinks that decision might be, Caldwell isn't saying much.
"One of the things, there's an old adage that you prepare for the worst and hope for the best," Caldwell said. "I think you always have to do that in our business."
If Suh is suspended, he would miss the Lions' wild-card playoff game against Dallas on Sunday. It also would mean Detroit would be without both of its first-round defensive tackle selections. Caldwell said Monday it would take "a miracle" for defensive tackle Nick Fairley to play against the Cowboys. Fairley has not played or practiced since injuring his knee against Atlanta in Week 8.
If neither Suh nor Fairley is available, the Lions likely would start C.J. Mosley and Andre Fluellen or Jason Jones at the defensive tackle spots.
After Sunday's game, without seeing the play on video, Caldwell said he believed Suh's ankle step was unintentional after others briefed him on it. He declined to give his opinion about his thoughts on Suh's ankle step during his weekly news conference Monday.
Caldwell said he spoke with Suh about it but wanted to keep those conversations private. In this case, Caldwell said his personal views on the play "don't matter."
"I did have a chance to look at it. We looked at it closely, and I had a chance to visit with him and all those kinds of things, which you would anticipate, you would expect," Caldwell said. "And the league's taking a look at it, and we'll see what happens and have a ruling about it soon."
This is a bit of a contrast to last week, when Caldwell defendedDominic Raiola's ankle stomp on Chicago defensive lineman Ego Ferguson. The stomp led to Raiola's suspension for Sunday's game against Green Bay. Raiola will be reinstated Monday, and Caldwell said he will be the team's starting center Sunday against Dallas.
In something that could come into play with Suh, the NFL suspended Raiola last week partly because of his previous actions.
Green Bay's players and coaches were not happy about Suh's actions after the Packers' win Sunday.
"I didn't see it live, I didn't see it on the JumboTron, but from what I'm told, I'm told it was ridiculous," Green Bay coach Mike McCarthy said Sunday. "There's no place for that. That's where I'm at with it. I don't understand it, frankly."
This isn't the first time Suh has had issues with Green Bay. He was suspended for two games in 2011 after stomping on the arm of then-Packers center Evan Dietrich-Smith. Suh was also fined $100,000 last season for an illegal low block on Minnesota center John Sullivan.
He has been fined for roughing up Cincinnati's Andy Dalton, Chicago's Jay Cutler, then-Houston quarterback Matt Schaub and then-Cleveland quarterbacks Jake Delhomme and Brandon Weeden.
Will Suh Be Suspended For Stepping On Rodgers?
Cris Carter and Mike Golic react to Ndamukong Suh stepping on Aaron Rodgers' lower leg twice during the Lions' loss to the Packers on Sunday.