Nobody stopped Saquon Barkley in college, and his linemen knew why. Can Panthers do it?

In 2015, when this season’s No. 2 overall NFL draft pick Saquon Barkley was a freshman running back at Penn State, the team’s offensive linemen knew before anyone else what he could be.

How?

“When I look at a back, I usually check out his legs and his calves first,” said starting center Angelo Mangiro at the time. “And then his (butt). And the kid, his attributes right there are phenomenal. Then you see spurts of, ‘Wow, this kid can be incredible.’ ”

The memory of it made current Carolina Panthers guard Brendan Mahon, who blocked for Barkley during a prolific collegiate career that included a Heisman campaign, laugh. Hard.

“And those big thighs,” he said this week. “He has that physical (build), you just take one look at him and you know he’s a special cat.

“He’s just a freak of nature.”

After the New York Giants, Carolina’s Week 5 opponent, drafted him, Barkley quickly earned the nickname “Saquads” on social media and his workout videos often go viral. Even at Penn State, he broke the Internet in 2016 by squatting seven reps at 495 pounds, a school record of any position at the time (he broke it the following year).

Barkley is strong, but he’s not just a power back. He’s shifty, a “jump-cut” back according to Panthers defensive coordinator Eric Washington.

So far this season, he has 260 rushing yards in four starts, including a 106-yard performance in Week 1 against Jacksonville, and three touchdowns.

And he catches passes. When former Penn State offensive coordinator Joe Moorhead brought the spread to the university for the first time, Barkley became much more than a downhill runner and was one of quarterback Trace McSorley’s favorite targets.

The idea was to get Barkley into space against a receiver, and let him get to work.

The Giants are doing the same thing. Barkley has 27 catches on 35 targets for 193 yards.

“The main thing is the ‘Uh-oh,’ that you see in those guys’ eyes when it’s one-on-one,” Mahon said. “A corner, a safety or a linebacker is one-on-one with him and has to tackle him in open space. You kind of see that ‘Oh, no,’ look in their eyes. And then he does his thing, and usually it’s taking it to the house. “

Even as a runner, if Barkley’s lanes aren’t eliminated, he is able to hit a hole and go into an elevated gear. One of Mahon’s favorite memories was a simple B-gap hole he helped open for Barkley in last season’s Fiesta Bowl. When Mahon looked up, all he saw were the numbers on Barkley’s back.

“I saw him break through,” said Mahon. “When you see him break through, you might as well run over to the sideline because you know he’s going to score.”

Barkley also is a patient runner who can navigate cutback lanes — if he has them.

“He operated a lot out of the gun at Penn State,” said Washington. “He can play behind the quarterback when he’s under center. He can do a lot of things. He’s a jump-cut back, which puts a lot of stress on the cut-back aspect of your defense because if you don’t have the right leverage against a cut-back, he can run around your defense.”

In Week 1, the Panthers had to overpopulate to the ball after initial contact and clog cutback lanes against Dallas running back Ezekiel Elliott. They were successful, holding Elliott to just 69 rushing yards. The two running backs drew comparisons from analysts before the draft. But Washington said this week that Barkley will still offer his defense something different than what they’ve seen so far.

“This young man is unique in his own right,” Washington said. “I mean, if you like pro football, if you like the run game, you’re going to like this guy.

“Now I don’t like him, because he’s on the other side. But I mean, he’s big, great contact balance. ... He’s already broken some runs. He’s going to be a tough guy to get down. We’ve got to suffocate him with as much population, as many bodies to the football (as possible).”