One reason the Eagles' running game worked so well against the Giants last Sunday was that Carson Wentz switched play calls at the line several times, after getting a good look at the defense.

"He checked to most of those run plays," running back Wendell Smallwood said after the Birds gained a season-high 193 yards on 39 carries. "He was seeing some things … he saw a favorable box, or he saw a scheme that would work for us. Some of the schemes, we hadn't done in a while. He checked to them and they looked pretty good."

This is one area where Wentz seems to be ahead of the curve, for a quarterback who will be making just his 20th NFL start Sunday at the Los Angeles Chargers.

Offensive coordinator Frank Reich said the coaches give Wentz "a lot of freedom; it's not unlimited freedom, though, "He has the aptitude to have as much freedom as you want … That's one of the reasons he's in this building."

Reich noted that Wentz exercised a lot of control of the offense at North Dakota State, one thing that impressed the Eagles in the scouting process.

Eagles coach Doug Pederson said Wentz can only change to something that is in that week's game plan, and usually, constrained by formation and personnel packages, he gets to the line and has one pass option and one run option.

"We have a system that I can get to anytime during the game. It's just a 'take it' system, that I can just give a formation and tell Carson to take it,"  Pederson said. "But there are parameters built around that based on the game plan, so that's the limited part. We don't give him full rein of our entire playbook. It has to be game-plan specific, and those specific plays are usually a one-run, one-pass in those situations."

Tight end Zach Ertz said there is no doubt that Wentz's ability to adjust at the line is helping the offense.

"I think he's earned it. He studies the heck out of the film, he dissects it himself, he understands, he puts himself in that situation before he even gets there. I think the coaches understand that," Ertz said. "They understand how involved and invested he is in that process. If I was a coach, I'd trust him wholeheartedly, too."

Center Jason Kelce said the Giants would try to disguise what they were doing by "bringing the weak safety down, then switching it at the last second, but he was right on top of it."

Kelce has been the starting center here since he arrived in 2011. He said Wentz has the most play-calling latitude of any QB he has snapped to; obviously, in Chip Kelly's hurry-up, the QB had almost no latitude.

"I thought Sam [Bradford] was a guy that probably could do something like this, but we just didn't do that [then]," Kelce said. "[Michael] Vick certainly had the ability to change the play … we just probably do a little bit more of it with Carson."

Right tackle Lane Johnson said Wentz sometimes makes simple adjustments, such as changing the side the run play is headed toward.

"If the number count's wrong [on the opposing front], he may switch it to the back side," Johnson said. "He's been doing that all year."

"Having the numbers be correct on a run play, you've still got to block it up right but it definitely sets you off on the right foot," Kelce said. "You're not running uphill, you're running downhill at that point."

Right guard Brandon Brooks said many of those adjustments were available to Wentz last season, even though he was a rookie.

"The difference is, he's faster with it," Brooks said, meaning Wentz is processing more quickly what he sees when he breaks the huddle. "When the ball's snapped, he knows exactly what it's going to be."

Pederson was asked when he determines he wants to just call the formation and leave the rest to Wentz.

"It's usually situational," Pederson said. "A lot of times, I feel like we want to go to tempo offense, we might start the first play with something like that, and give him a take-it call by formation … could be in the big red zone, it could be out in the normal field anywhere, and just [depend on] the feel and flow of the game."

Wentz said sometimes a play is relayed to him with the understanding that it will only work if the defense presents the anticipated look.

"There are certain play calls where from the beginning, it's, 'We're going to call this play, but if you see something, get us out of it,' " he said.  "There's other times where I just see something in the defense. We don't have the whole playbook at our disposal, but it's something we've definitely worked on in the offseason, and more than anything, talked through when we're in meetings and watching film.

"I think they have a lot of confidence in me to get us in and out of the right plays. That was something we utilized a little bit on Sunday, and I thought it was effective."

It will be interesting to see if Wentz is able to do the kind of adjusting he did against the Giants again this week, battling the noise of a hostile crowd. Running the ball ought to once again be important, against a Chargers' defense that has two elite pass-rushers in Joey Bosa and Melvin Ingram, but ranks 31st against the run through three games, 27th in yards per carry allowed.

"Everybody has to just echo the call," Kelce said. "We've done that both on the road and at home. The biggest thing on the road is trying to communicate it across the board; sometimes it takes more time to do that, and then you run into play clock situations."