The Florida Gators are unsure when starting running back Matt Jones’ viral infection will pass, but even after the doctors clear him, it might take a while to get back in football shape.

“Our physicians have told me we’re in a little bit of uncharted waters here about him coming back and when that’s going to happen and how good of health he’s going to be in,” coach Will Muschamp said. “I don’t know any of that right now. It’s very uncertain. It’s very frustrating, for him first of all, and for us a little bit.”

That means it is too early to tell if Jones will be ready for the season opener Aug. 31 against Toledo. Muschamp confirmed that the sophomore has lost weight because of the illness, but was unsure of the exact amount.

Jones ran for 275 yards and three touchdowns on 52 carries last year. Muschamp said throughout the offseason he expected a breakout year by Jones as he replaces Mike Gillislee. Gillislee, now with the Dolphins, rushed for 1,152 yards last season.

Mack Brown, a redshirt junior who has 40 career carries, now holds the No. 2 spot. The remainder of the reps will be split among walk-on Mark Herndon and true freshmen Kelvin Taylor of Bell Glade and Adam Lane. The Gators also will use fullback Hunter Joyer and receiver Trey Burton.

Injury update: Several Florida players sat out the first day of training camp, but there were no new injuries. Three starters — quarterback Jeff Driskel (appendectomy), guard Jon Halapio (torn pectoral muscle) and guard Max Garcia (back) — hope to return by the end of next week.