In the win, Ryan Mathews only carried the ball twice, losing five yards on the rushes, before not being used after the first quarter. Wendell Smallwood and Kenjon Barner carried the majority of the workload on the ground.
Pederson said Monday that Mathews was used so scarcely because the ankle injury he's been dealing with, on and off, since before training camp "never loosened up" for him before the game Sunday.
Mathews' right ankle, the same one which was rolled up on in the Eagles' first game of the season, was the problem for the 28-year-old running back.
"It was stiff, so we just opted on the side of caution more than anything else," Pederson said.
During the week leading up to the Steelers game, Pederson said the team would be open to using a sort of rotation system at the running back position, which is essentially what they did on Sunday.
However, when asked about how he would treat the running back position when Mathews is fully healthy, ideally after the bye week, Pederson said Mathews is still the team's primary running back.
"When Ryan's healthy, he's the guy," Pederson said, "and then we'll mix Darren in there, too. And you saw what Wendell can do, and you saw what Kenjon -- Kenjon, we know what he's all about.
"Everybody's a little different runner. Wendell did an excellent job between the tackles last night, sort of downhill, Kenjon did a nice job outside the tackles, and of course Darren can kind of do everything. We'll still keep the rotation the same, we're not going to change much that way. We just want to get everybody in the football game."
Mathews ran the ball 22 times in Week 1, which seemed a bit high at the time, and still seems so in retrospect, but Pederson said he was happy with the number of carries Mathews saw that game.
"I think that's a good number for him, honestly," Pederson said. "And then if everyone can get a few touches after that, you're on track."