That next man at the running back position is Fozzy Whittaker. On Sunday, Whittaker rushed for 100 yards on 16 carries in the Panthers' 47-26 win against the San Francisco 49ers.
Rivera contends that Stewart will miss at least a week or more. He suffered the injury in the first half. The team is awaiting the results of Stewart's MRI.
Stewart signed a five-year, $36.5 million contract extension in 2012. Since then, he has never played a full season. He has suffered numerous foot and ankle injuries along the way.
"We've got some good backs," wide receiver Philly Brown told the Charlotte Observer. "Hopefully Stew comes back, though – quick. But Fozzy and those boys are good."
The Panthers face the Minnesota Vikings Sunday at Bank of America Stadium.
"I've got a tremendous amount of faith in who CAP can be for us."— Max Henson (@PanthersMax) September 19, 2016
With Stew hurt, Rivera updates the RB situation: https://t.co/MCmuxMm7MK
"I had a lot of confidence in all of them, really,'' Panthers offensive coordinator Mike Shula told ESPN's David Newton. "Those guys are really well prepared, so we'll probably do it like we did it last time. Cap will be ready. Fozzy and Mike, and we've got that other guy back there that can carry it a couple of times, too.''
Rivera said that he "feels good" about Stewart's replacements.
"If it's a hamstring, which every indication points to that, it's going to be at least a week," Rivera told reporters. "We'll see how severe. He said he felt pretty good walking around when I ran into him just a second ago.
"The one thing we've been able to do the last few years here is we've been able to replace guys when they're out. We've had a next-man-up mentality that's been very beneficial for us, and this is one of those circumstances. If Jonathan is out for an extended period, we feel good about the combination of guys we have."
The Panthers will also look to fullback Mike Tolbert and Cameron Artis-Payne to plug in for Stewart.
When Stewart sat out three games to close the 2015 season, Artis-Payne had 152 yards on 33 carries. Tolbert had 115 yards on 24 carries during that stretch.
Try to stay clear of this situation on your fantasy football team. None of these options offer consistent RB2 value but could be valuable in deeper leagues.
Stewart earned his first Pro Bowl bid in 2015, handling a career-high 242 carries for 989 yards and six scores on the ground. He also had 16 receptions and a receiving score last season. This season, he has rushed for 73 yards on 20 carries.