San Francisco 49ers fullback Kyle Juszczyk has a new teammate in the running backs room in rookie Kaelon Black, one of the team’s third-round picks.

While Juszczyk has yet to see Black face an NFL defense, he’ll get an early preview when the 49ers begin organized team activities next week. Even so, the veteran has already been impressed by the rookie’s physical build.

“Kaelon is absolutely jacked,” Juszczyk said on The Rich Eisen Show. “I don’t know if you’ve seen this guy.”

According to Juszczyk, Black’s physique even stacks up against one of the more impressively built players in the locker room.

“Malik Mustapha walks around in the locker room, and this dude’s just like an absolute ball of muscle,” Juszczyk said. “You can’t believe he plays safety. He’s one of the biggest dudes you’ve ever seen.

“And this week, Kaelon’s walking around with his shirt off. I’m like, ‘Malik, you’ve got major competition now.’ I think this might be the new most muscular guy in our locker room. So hopefully, he plays as good as he looks.”

Juszczyk is also familiar with Black’s production at the college level. The rookie contributed to Indiana’s national championship run last season, finishing with 1,040 rushing yards and 10 touchdowns while sharing carries in the backfield.

“I’ve seen highlight clips of his running and been super impressed,” Juszczyk said. “And I know people have kind of mentioned that he didn’t catch a lot of passes at Indiana, but you wouldn’t be able to tell that based on what you see on the practice field.

“He looks very natural running his routes, very natural hands, and I think he’s going to fit in just perfectly.”

Black’s selection in the third round drew attention, as he was projected to go later in the draft and was not invited to the NFL Scouting Combine. Still, Juszczyk pointed out that pre-draft expectations don’t always define NFL success.

Eisen pointed out that Juszczyk himself went undrafted out of Harvard before becoming a multiple-time All-Pro and Pro Bowl selection.

“I’m definitely going to bring that up this week because, like you said, we’ve got that in common,” he said.