Caldwell said, however, that all the players on his roster would get an equal chance to impress and that he was not going to take last season into account too much.
"I'm not certain," Caldwell told the club's official website. "You're never 100% certain about anything, you know? I can't be certain if I'm going to wake up tomorrow morning.
"Tomorrow's not promised to me, so I'm not certain. We'll see. He's a young man and typically they heal pretty quickly, unlike old guys like me. But we anticipate that he'll come along. We'll have to wait and see.
"As a matter of fact, I haven't dwelled on last year as much. We looked at it from a technical standpoint, just to know that we were aware in what they can do, appears that they can do. But we wanted to start from a clean slate out here and give everybody an opportunity to start from scratch and see what they have."
The Lions finished with a 7–9 record last season and came third in the NFC North.