Running back Rashaad Penny had the best day of his young career for the Seattle Seahawks on Sunday. Against the Philadelphia Eagles, Penny had 14 carries for a career-high 129 yards. Inside those numbers are some significant plays, like a 21-yard gain in the 4th quarter that paved the way for his 58-yard run right into the end zone.

Who or what does Penny credit for his incredible day? McDonald’s. Or the absence of McDonald’s, to be more precise.

“I stopped eating McDonald’s,” Penny said at the news conference following the Seahawks’ 17-9 win over the Eagles. “That was hard for me. But then I just got serious about football. Having a great body weight and body shape takes you a long way as a running back. I’m learning that from Chris [Carson], trying to be in his shoes.”

Rashaad Penny says cutting McDonald's out of his diet helped him have a career day against the Eagles. (Photo by Mitchell Leff/Getty Images) More

What made Sunday even sweeter is that Penny had been struggling. Fellow running back Chris Carson has been outstanding, which means there hasn’t been a lot of playing time for Penny. And when he did play, he wasn’t dynamic. He had 14 carries total over the five games before the Week 12 matchup against the Eagles. In Seattle’s previous game against the San Francisco 49ers, he played just three snaps and fumbled the ball for a turnover.

The Rashaad Penny we saw on Sunday didn’t look like the same guy who fumbled against the Niners. With him crediting his monster day to an increased focus on nutrition and health, hopefully we’ll see more days like that from him over the last five weeks of the season — and possibly into the playoffs as well.

More from Yahoo Sports: