Christian McCaffrey gives an update on his calf injury

49ers running back Christian McCaffrey won't play in the preseason after straining his calf in Sunday's practice. He has not participated in practice since.McCaffrey, though, said his rehab is strictly precautionary."Yeah, I feel great," McCaffrey said on SiriusXM NFL Radio on Friday, via 49erswebzone.com. "Very cautionary stuff. If we had a game, I would play, but just trying to be smart right now. But still training, still getting a bunch of work in, so that come Week 1, we're ready to roll."McCaffrey, the NFL's reigning offensive player of the year, could take another week to rehab before returning to get ready for the Sept. 9 season opener against the Jets.He had a career-high 417 touches last season, including the postseason, so the 49ers were giving him regular rest in training camp anyway and likely will continue to do so during the season.