Through four games, Eagles rookie Derek Barnett probably hasn't shown up on the stat sheet the way many fans predicted or hoped. 

He hasn't made any mistakes either.

"He's had very few missed assignments," defensive coordinator Jim Schwartz said. "I don't want to give gold stars for that because that's what expected of us. But I think that's also a good sign coming from a rookie that's getting significant playing time, specifically in some key situations." 

The numbers aren't there yet, though. The 14th overall pick doesn't yet have a sack; he has six quarterback hurries and one quarterback hit. He has just five tackles. 

But as always, the numbers don't tell the whole story. Schwartz said on Tuesday that Barnett has had an up and down first four games but played a better game against the Chargers. Barnett had an impact on Sunday in the Eagles' 26-24 win. 

And even when he didn't, he was showing off one of the traits his coaches absolutely love: his motor. 

Let's take a look at the rookie's performance on Sunday: 

This is Barnett's second snap of the game, and it comes on the very first drive of the game. The previous play was an incompletion. On this one, Barnett is lined up against former Pro Bowler and Super Bowl champion Russell Okung. And Melvin Gordon in the backfield is going to offer Okung some help. 

Barnett does something he hasn't done much of yet this season. For most of his first three games he's relied on his quick outside pass rush. Not this time. On this play, Barnett uses a simple bull rush against a pretty good left tackle. There's a chance Okung just wasn't ready for Barnett to go with a power move. 

But it works. Barnett pushes Okung back into Philip Rivers' grill. Rivers feels the pressure and is about to escape the pocket. On the back end of the play, you'll see Chris Long begin his pursuit from behind. 

Barnett already did his first job on the play. His pressure set it up. But as Long is about to get a strip sack, the rookie never stops his pursuit. We've seen this on Barnett's film from Tennessee and the preseason. He never gives up on plays and he actually has the speed to get back in a lot of them. Barnett's hustle on this play gives him his first fumble recovery of his young career. And this play was huge. It gave the Eagles a short field for their first touchdown and completely altered the momentum. 

OK, so this isn't ideal. On this play in the second quarter, Barnett is lined up in coverage in the slot against Keenan Allen, who just happens to be the Chargers' best receiver. That's an obvious advantage. Allen was motioned into the slot just before the snap. The Eagles at times like to use these zone blitzes and this time, Jordan Hicks is going to rush. 

Schwartz said the Chargers caught them in a motion. The Eagles had actually changed their blitz specifically to avoid that situation, but they were stuck. 

"As soon as I saw that matchup, I was like 'oh my gosh,'" Schwartz said, "but he was the right guy to have out there."

Once Rasul Douglas sees Antonio Gates start to run a shallow slant, he drives. That is going to leave a lot of space to that side of the field. Still, Barnett has pretty tight coverage. 

Rivers just has to wait for the play to develop. While Barnett offers good coverage early, he knows Allen is going to be able to speed away from him. The Chargers' offensive line does a great job of picking up every hat, including Hicks, who was coming on the blitz. It looks like Long might have a case that he was held. Oh well. 

"I'll tell you what, [Barnett] did a good job of getting that," Schwartz said. "We didn't get enough pressure. He shouldn't have to cover for that long. Obviously it's a zone blitz and he shouldn't have to cover for that long." 

Barnett actually does a pretty decent job of covering Allen, but he just had no real chance to cover him for that long. Allen catches a 21-yarder to move the chains, but Barnett never completely lost him and is able to tackle him. "It certainly showed his athletic ability and his speed," Schwartz said. 

Obviously, the Eagles shouldn't want to have Barnett on a WR1. That can be an obvious downside when a receiver lines up inside during a zone blitz. But the athleticism Barnett showed on this play should allow Schwartz to use zone blitzes with him in the future. He might not be able to cover Allen for an extended period of time, but a tight end is a different story. 

It obviously won't become his full-time role though. 

"We didn't draft him for coverage," Schwartz said. "We drafted him to rush the passer." 

I think the most impressive thing about this series wasn't that Barnett had decent coverage on a really good receiver. It was that on the very next play, after running down the field 21 yards to make a tackle, Barnett came back and picked up the second tackle for loss of his young career. 

With Okung on him again, Barnett shows good get-off at the line. Okung doesn't get much of him before turning his attention to a charging Nigel Bradham. But Gordon isn't going to get that far. 

Barnett gets in the backfield and blows up the play. On the next snap, Beau Allen tackles Branden Oliver for a five-yard loss; Barnett had good push on that one too. 

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No, Barnett isn't getting sacks yet. And, no, the Eagles didn't draft him with the 14th pick to get just a hustle player. But eventually, the sacks should come. And if they don't, it won't be for lack of effort. That motor is running at full force.