ANAHEIM, Calif. – Chris Long was impressed with Aaron Donald long before the guy ever recorded his first NFL sack, and long before he earned the first of his three-and-counting Pro Bowl invitations.

"I remember his first training camp when he was a rookie (in 2014),'' said the Eagles defensive end, who was Donald's teammate for two seasons with the Rams. "I'd be the last one out of the building in camp.

"I'd go in to watch film, and he was always hogging the video machine. I'm like, who taught this guy how to watch tape and how to prepare? It was like he was a ready-made pro.''

The Rams, who will take a 9-3 record into Sunday’s important NFC matchup with the 10-2 Eagles, have made their fair share of personnel blunders over the years, a big reason that they haven’t made the playoffs since 2004. But selecting Donald with the 13th overall pick in the 2014 draft wasn’t one of them.

In just his fourth pro season, the 6-foot-1, 285-pound Donald is regarded as the best interior defensive lineman in the league. His 70 total quarterback pressures this season, including eight sacks, are the most in the league by a defensive tackle or 3-4 end. The Bengals' Geno Atkins is a distant second with 58. The Eagles' Fletcher Cox has 40.

Donald has at least one sack in six of the Rams' last seven games. He has 43 tackles, including 25 solo, and 13 tackles for losses. No one else on the Rams has more than seven. He also has a team-high three forced fumbles.

"He's definitely one of the best interior guys in the league,'' said Eagles left guard Stefen Wisniewski, who is the lucky guy who likely will be spending the most time trying to block Donald on Sunday.

"He's a really elite talent. Very quick. And he plays hard. He has a wide repertoire of pass-rush moves. He's got power. He's got speed. He's athletic. He's got it all. Definitely have to be at your best to handle a guy like that.''

Donald has made a seamless transition from the 4-3 scheme the Rams played the last three years under Gregg Williams to the 3-4 they now play under Williams' successor, Wade Phillips. The scheme switch really didn't affect Donald much. He played three-technique (the gap between the guard and tackle) in Williams' 4-3 and is playing mostly three-technique in Phillips' defense.

He'll move around some, but mostly will line up on the right side of the defense.

Donald's marginal height was a little bit of a concern when he came out of the University of Pittsburgh. He won just about every national defensive award in his final year at Pitt, including the Outland Trophy and the Bednarik Award. Players can add weight and strength at the next level, but unless they have a rare late growth spurt, they usually aren't going to get any taller.

Just based on talent, he should've been a top-five pick in the '14 draft. But the size concerns kept him on the board until the Rams took him at 13.

Even the Rams had reservations about his height. They had the second pick in that draft as well as the 13th. They took offensive tackle Greg Robinson with the first pick. Robinson turned out to be a bust. The Rams finally palmed him off on Detroit in June for a sixth-round pick. But they got Donald right. Very, very right.

"Aaron Donald is spectacular,'' Long said. "I think a lot of people this year, now that he's in a big market, are finally realizing how good he is.

"He's short, so he has good leverage. I don't mean that to slight him. But he's got long arms (32 5/8 inches). So it's like he's 6-6. He's extremely twitchy. He works as hard as anybody in football.

"When you combine his physicality, his work ethic, his instincts, I mean, it makes for a damn near perfect player.''

Donald is going to make some plays Sunday. He spearheads a Rams pass rush that is third in the league in sacks with 37.

But they have struggled against the run. They're 27th in rushing yards allowed per game (122.8) and 30th in opponent rush average (4.7).

Wisniewski expects Donald to line up across from him a good portion of the game.

"He'll definitely play a little bit on the other side as well,'' he said. "Generally, in their base defense, he plays away from the strength. We'll have the strength set both ways. So he'll play both ways I'm sure in base. But he'll probably be more over me.''

He is looking forward to the challenge.

"Definitely,'' he said. "It brings out the best in you. For myself, you really find out how good you are when you're playing against the best.''

Wisniewski doesn't get the acclaim some of his offensive linemates do. But he is quietly having a solid season, particularly in the Eagles' run game, which is No. 2 in the league. And you can bet the Eagles will be running the ball a lot Sunday.

"I think Wiz is a really, really good player,'' center Jason Kelce said. "I'm confident with Wiz up against anybody, including Donald. He'll do a good job.''