Coach Bruce Arian confirmed that running back Rashard Mendenhall (knee), wide receiver Andre Roberts (quadriceps), tight end Rob Housler (high ankle sprain) and nose tackle Dan Williams (low-ankle sprain) all will undergo MRIs for injuries sustained Saturday night, according to the Cardinals' official website.
After missing a portion of training camp because of patellar tendinitis, Mendenhall felt looseness in the same right knee, forcing him from Saturday's game. Mendenhall suffered an ACL tear to that knee in the 2011 season finale.
The severity of Mendenhall's setback is not clear. The timing couldn't be worse, as he appeared to be running with more juice than he had since back-to-back 1,000-yard seasons in 2009 and 2010. Mendenhall is averaging 6.1 yards per rush on 13 carries over the past two weeks.
If there's a sliver of good news, it's that Ryan Williams said he was "fine" after rushing for 10 yards on two carries in his 2013 preseason debut. Williams had been sidelined by a patella injury of his own.
Should Mendenhall miss extended time, the Cardinals likely would turn to a committee featuring some combination of Williams, Alfonso Smith, Stepfan Taylor and Andre Ellington. There's no clear-cut No. 2 in this backfield.