Cunningham said that in pre-season Bentley has a lower offense success rate against him than the NFL's best, and urged the player to keep the effort up.
"Bill Bentley's the hardest-working guy on our team and it's showing," Cunningham told the Lions' official website.
"The first week, the offence has 25% success. Well, Ike Taylor's the number one guy in the NFL with 39.9%.
"If he keeps going at this pace, you've got a guy that can cover. That statistic may not mean much to some people, but to a coach it means a lot, because he's competing every day."
Bentley, a rookie last season, made just four appearances in his first year in the NFL.