The San Francisco 49ers got a much-needed win at the start of their bye week on Sunday night, defeating the Dallas Cowboys 30-24 to move to 4-4 at halftime.

It was an eventful night as the 49ers started slowly and Dallas took a 10-6 halftime lead. But a 21-point third-quarter performance led the way as San Francisco held off a final comeback to win.

But en route to the hard-fought win, the 49ers once again faced adversity and dealt with some injury issues as running back Jordan Mason was unavailable after a few rush attempts early in the game.

Mason, who was dealing with a shoulder injury earlier in the week, didn’t play the entire second half, which led to fourth-round rookie Isaac Guerendo taking over the leadback role in an important situation.

Guerendo started the year slowly as he battled several injuries and hadn’t really achieved much success until San Francisco’s Week 6 game against the Seattle Seahawks, when he finished the game with a 76-yard rush.

But on Sunday, Guerendo had his biggest role yet, rushing for 85 yards and a touchdown on 14 attempts and taking the lead in the second half as San Francisco went on a big scoring spree.

How did the rookie overcome the 49ers’ challenge?

“I thought he did a great job,” head coach Kyle Shanahan said of Guerendo. “He came in, he was ready to go. JP got screwed, JP tried to come back and maybe could have, but Isaac got going and did a good job.”

“I think he learned something from every run he did. There were a few runs at the start of the year where he did quite well, but we rate him as pretty tough, all of them pretty tough. And he had a couple, like four-yard runs, where we thought he could have gotten seven yards. We’re pretty hard on him. And then you see how he translates that into training and everything that we really pushed him with, he was really coachable, he’s not a sensitive guy, he’s very detailed and he’s very well prepared for a rookie. Things aren’t too big for him and he didn’t see much in the preseason, but after getting healthy there and over the course of this year, I feel like he’s gotten better every week.”

Even after the win, the running back focused on areas where he could improve, which was well received by the coaching staff.

“There is always room for improvement,” Guerendo said. “Being able to look at that again and fix those little things – all those little details. We have a great (running back) room. Being able to ask these guys questions was obviously a really big deal for me as a newbie in the room. I’m grateful for them, grateful for my coach and I appreciate them all.”

Quarterback Brock Purdy praised his running back and pointed to his willingness to learn as a key reason for his rise up the depth chart.

“Yeah, I’m really happy for him,” Purdy said of Guerendo. “The way he comes to work every day and stuff and the chip he carries on his shoulder, humble guy. He constantly asks questions and wants to make sure he’s doing everything right. For him to do what he’s doing for our team right now, I couldn’t be happier for him. And I get it, man, when you come in as a freshman with a few guys on the team and some big names on the squad and everything else, you can be in awe in a way, but when he comes in, he doesn’t care. He grabs the ball and runs hard, that’s what I like about him.”

San Francisco enters the bye week with a chance to regroup across the board as running back Christian McCaffrey could return for the first time this season.

But they needed Guerendo to get the win on Sunday night, and the rookie came up big off the bench.