ARLINGTON, Texas -- A month ago, Aaron Jones was the Green Bay Packers' fourth-string running back.

And the prize for that is a spot on the game-day inactive list.

That’s how the rookie started the season in the Sept. 10 opener.

How quickly things can change in the NFL. In Sunday’s 35-31 win over the Dallas Cowboys, no one made a bigger impact than the fifth-round pick from UTEP with his 125 yards and a touchdown on 19 carries.

Aaron Jones rushed 19 times for 125 yards and a touchdown in Sunday's win. Matthew Emmons-USA TODAY Sports

Jones didn’t even line up from scrimmage for the first time until last week after Ty Montgomery broke multiple ribs and Jamaal Williams dropped out with a knee injury. It was at that point against the Bears that coach Mike McCarthy had no choice but to turn to Jones.

McCarthy liked what he saw so much last week, when Jones rushed for 49 yards and a touchdown on 13 carries, that he bypassed Williams, who returned against the Cowboys, and started Jones in place of the inactive Montgomery.

McCarthy didn’t just start Jones, he rode him.

"Very proud of Aaron Jones," McCarthy said. "Earned the opportunity to start, and he produced, and that’s what you look for in all your players, especially your young guys. You know, this was his first chance to take a big load in the run game, and I thought he played outstanding. I love his running style, very productive. Great job."

The diminutive Jones (5-foot-9, 208 pounds) showed some quickness this preseason when he was the Packers’ leading rusher, albeit McCarthy didn’t run the ball enough to have a great feel for any of his three rookie backs. And that quickness was apparent when it mattered. He hit holes quickly, and even if he didn’t always make the right read or cut, he did so decisively.

“It was a little nerves; just didn’t want to make any mistakes,” Jones said. “Ty told me before the game, he was like, ‘Nobody plays a perfect game. If you’re going to make a mistake, make it fast. That will make up for it.’ I did make a mistake, and I made up for it by playing fast.”

Jones said that came on his lone reception of the game. He said he ran the wrong route but still ended up turning into a 9-yard catch.

His 22-yard run in the third quarter that set up the go-ahead touchdown was the Packers' longest rush of the season and their first more than 20 yards. All but three teams had at least one 20-plus-yard run this season before the Packers got that one from Jones.

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To cap it off, Jones sliced his way for a 15-yard run on the Packers’ game-winning drive to at least put them into position for a field goal that would have forced overtime. But the Packers didn't need overtime because Aaron Rodgers and Davante Adams won it with a 12-yard touchdown with 11 seconds to play.

This is why Ted Thompson picked three running backs: Williams in the fourth round, followed by Jones in the fifth and Davante Mays in the seventh. It was Mays who was active and ahead of Jones in the season opener.

"I told him before the game, I have absolutely zero worries about him back there," Rodgers said. "He is a great kid. He’s a rookie, but his vision was fantastic. He gives you a lot of confidence that we can give him the ball on the last drive. Not only does he get through the line and make a nice run, but the kid runs out of bounds. That’s stuff you can’t coach. You love the instincts there. He’s a talented guy. I’m really proud of him. Big step today for him."

Yes, the Packers have all kinds of problems -- their offensive line still isn’t intact, and their defense couldn’t get that one last stop it needed when it allowed the Cowboys to go 79 yards on 17 plays over 8 minutes and 43 seconds to regain the lead with 1:13 left -- but now know they have plenty of depth even when Montgomery returns that perhaps they can finally field a one-two punch that McCarthy prefers over a workhorse back. They also can afford to let Montgomery’s ribs fully heal rather than him trying to play with a protective vest like he tried in practice last week.

The Packers have been ravaged by injuries this year, but at least it doesn’t appear they’ll run out of running backs like they did last year -- when they had to move Montgomery from receiver. And they have Jones to thank for that.