Prior to his interview with Lions brass, Caldwell charted every one of Stafford's 2013 passes. He then diagnosed what went wrong and told the staff where he could help the quarterback improve, NFL Media Insider Ian Rapoport said Saturday on NFL Network's "NFL GameDay Morning."
Caldwell also watched film with Stafford and offered corrections on throws, Rapoport said.
The Lions are taking Caldwell's candidacy for their coaching vacancy seriously and are calling around looking at his reference, according to Rapoport. Peyton Manning has long supported his former coach.
It's telling that Stafford is part of the hiring process. Stafford might not be able to pick his next coach, but his inclusion in the process signifies the team's recognition that the quarterback's improvement is one of the most important aspects of the coaching search.
UPDATE: Ken Whisenhunt is a top choice for the Lions, Rapoport said later on "NFL GameDay Morning." The quarterback-friendly coach should interview this week, according to a team source. The Lions spent the last week doing research on him. If Whisenhunt ends up with the Lions, veteran offensive line coach Russ Grimm could join him, according to Rapoport.