"I didn't know it," Zwinak said. "I turned around, looking for [the ball], and thought I missed it. Then I turned around, saw him running with it, and thought: 'Oh, thank God.' "
The score was the game's last, as Penn State defeated Purdue, 45-21, on Saturday at Beaver Stadium. Zwinak ran for three touchdowns and 149 yards, despite not getting the start.
Starter Bill Belton's second-quarter fumble was canceled out by an ensuing interception by Penn State cornerback Jordan Lucas. Zwinak replaced Belton on the following drive, rushing on five of six plays for 39 yards and a touchdown.
The Nittany Lions ran the ball 58 times in contrast to just 23 pass attempts.
"As long as the team is moving the ball, it doesn't matter," Zwinak said. "But as a running back, you're obviously going to want [the team] to run the ball. . . . It was definitely nice seeing them call the run that many times."
O'Brien said earlier in the week that Penn State's running backs carry "the hopes and dreams of this football team," and that was evident by his ground-heavy approach to Saturday's game.
However, when Belton and Zwinak each put the ball on the ground against the Boilermakers, O'Brien's exasperation was palpable from the sidelines. Penn State recovered Zwinak's fumble.
"It's frustrating because they're good players and great kids," the coach said. "Better kids than they are players. They feel bad about it, and I feel bad about it.
"You don't want to overemphasize it, because then you got the guy thinking about it all the time. But we've got to stop putting the ball on the ground. That's the bottom line."
For the most part, Zwinak put those struggles behind him over the Lions' last two games. His fumbling issues aside, he has still excelled in his brutish running style, carrying would-be tacklers several extra yards before finally falling down.
"Zach's a levelheaded kid," center Ty Howle said. "He comes in with the same mind-set every week, that he's going to run as hard as he can, whether he has 40 carries or 10 carries. He's going to make those carries count, break tackles, and hit the hole. He had a great game, and he does what he always tries do."