This has been a particularly taxing offseason for Brian Calhoun, who has been rehabbing a knee injury. Sunday, though, he pronounced himself fit and ready -- "I'm 100 percent'' -- for the physical challenge and punishment of another training camp. And when the Detroit Lions report on July 25, he will have plenty to prove, since he was limited to just seven carries during a rookie season that ended abruptly last November. During an individual blitz pickup drill in practice, Calhoun's knee buckled and he tore his anterior cruciate ligament."I felt like I was beginning to make strides at the end of the year before my injury,'' said the 5-foot-10, 208-pound Calhoun, a third-round selection (74th overall) in the 2006 draft. "I feel like I can play in this league. I know I can, and I know I can play for a long time. But once you do have an opportunity, once that window opens and you get that chance to prove yourself, you have to show what you can do in that limited time and, hopefully, the rest will take care of itself.''There will be no shortage of competition at running back for the Lions, who acquired Tatum Bell from Denver in a trade and signed free agent T.J. Duckett, the former Michigan State star. The team's leading rusher, Kevin Jones, is expected to regain his starting assignment once he's completely healed from a foot injury. But there is no timetable on his return. Shawn Bryson, a nine-year veteran, is also in the mix. "It will be kind of a free-for-all for reps in training camp,'' Calhoun conceded. "It's all about helping our team win, and it's going to take more than one of us (to man the position). It should be a battle to see who's the best running back. Some guys are not going to make it, some guys are.''In making decisions, Calhoun has always tried to be pragmatic. Like he was about declaring for the NFL draft and leaving Wisconsin with a year of eligibility remaining. "Hindsight is 20/20,'' he said. "I could have come back to school and maybe we could have won the national championship and maybe I could have won the Heisman Trophy. But I thought it was the best decision for me at the time. Who knows? I could have come back and got hurt during spring ball or fall practice or even during the season.''That's the example that Calhoun cites whenever people ask whether he has any regrets about his decision in light of his unproductive first season in Detroit. "If I had tore my ACL at Wisconsin the same time I did in the NFL -- which would have been late in the college season -- where does that leave my future?'' Calhoun posed. "It was the best decision and the most solid decision I could make at the time. Of course, when you look back, they (the Badgers) did have an amazing season.''Calhoun expects more out of the same from Wisconsin, even though questions have been raised about John Stocco's replacement at quarterback, whether it's Donovan or Allan Evridge, or both. "Tyler showed last year he could be a starter and win games,'' Calhoun said. "And the more he plays, the better he will get.'' Not unlike his situation in Detroit? "I felt like I belonged there (NFL) last season,'' he said, "and I'm looking forward for the opportunity, that small window, to prove to everybody that I can play in this league.''