One of the most hyped fantasy prospects of the summer, McKinnon caused many people to hold their breath when he went down in practice Sunday -- and probably no one more so than 49ers coaches who already are without Matt Breida's services for a few weeks due to a separated shoulder. Thankfully, early reports revealed that McKinnon is only dealing with a calf strain and San Francisco is taking a week-by-week approach with him. With Breida also sidelined, though, we're now going to get a good long look at Raheem Mostert, Joe Williams and Jeremy McNichols. Given the two-back system head coach Kyle Shanahan is expected to deploy, one of these guys could attain fantasy relevance if either McKinnon or Breida miss time during the regular season. In other news, here's what's happening elsewhere around the league:

• Buffalo: Josh Allen's time to shine might be here sooner than expected, as both AJ McCarron and Nathan Peterman exited Sunday's practice with injuries. McCarron reportedly had his leg stepped on while Peterman fell awkwardly on his shoulder. There's been no indication that either is dealing with anything severe, but all of a sudden there's a nonzero chance that Allen will start Buffalo's second preseason game this Thursday against the Chargers.
• Green Bay: A number of key offensive players returned to the field Sunday, starting with Randall Cobb, Jimmy Graham, and Aaron Jones. Cobb is still working his way back from June surgery on his ankle, Graham is dealing with a minor knee injury, and Jones missed a good portion of training camp with a bum hamstring. Of the bunch, Cobb's situation seems most worrisome, though that could change if the 31-year-old Graham continues to miss time in advance of Week 1.
• Pittsburgh: James Conner exited Sunday's practice with an unspecified groin injury, which could give Jaylen Samuels the crease he needs to seize the No. 2 role if Conner is forced to miss extended time. Given the significant offensive role Le'Veon Bell controls in the Pittsburgh offense, whoever earns the backup running back title will quickly become one of the most coveted handcuffs leaguewide.
• New England: It looks like the sore back that Tom Brady has reportedly been dealing with is nothing to be overly concerned about. That said, there's a chance we haven't heard the end of this situation.