PHILADELPHIA -- In describing the development of Carson Wentz, Philadelphia Eagles quarterbacks coach John DeFilippo pointed to a third-down play early in the game against the Buffalo Bills Thursday. There was a "route error" on the outside. Recognizing this, Wentz calmly reset his feet, slid to the right and connected with tight end Zach Ertz for an 11-yard gain, which ended up being a yard short of the sticks. The fact that Wentz didn't panic and quickly executed Plan B was a sign of maturation within the system, DeFilippo said.

The miscue at the beginning of the play, meanwhile, spoke to how green Wentz's top projected target, Alshon Jeffery, remains when it comes to working in this offense.

The route error was Jeffery's. He was supposed to run a corner route but instead ran an out.

"Alshon ran the wrong route. Probably a route that he hadn't practiced yet," said receivers coach Mike Groh. "Certainly his responsibility to know it, but in a short week, in a non-game plan week -- ordinarily you're spending four days of practicing and game-planning a team, you'll run every play. And that's one that's been up but because of the time that he missed, we had it up two different ways and he got confused."

Thursday was Jeffery's unofficial debut in an Eagles uniform. He was sidelined for the preseason opener against the Green Bay Packers because of a shoulder strain, an injury that sidelined him four straight practices. It was about another week-and-a-half before he returned to team drills. Focused on getting him to the regular season healthy, the Eagles' brass took a conservative approach. Now they have to concentrate on getting him up to speed.

"I think he's behind," said Groh. "Anytime you miss the amount of time that he did, he's a little bit behind. Fortunately we have time for him to catch up. I thought they got off to a great start the other night."

Wentz and Jeffery failed to hook up on the first two tries Thursday. The original plan was to only play Wentz and company a series or two, but with the offense sputtering, head coach Doug Pederson decided they needed more field time. They finally got things going on the fourth drive, as Wentz connected with Jeffery for a 9-yard gain and then again on a slant that went 14 yards two plays later.

"It was good to get him out there and finally get some opportunities to get some completions with him," said Wentz.

The two had a chance to work with one another through the spring, and then again during the break before training camp back in Wentz's home state of North Dakota. The opportunities have been lacking over the last several weeks, however, and as Thursday demonstrated, there's plenty of wrinkles that still need to be ironed out between now and the season opener at the Washington Redskins Sept. 10.

"I don't know if there's an exact time [a quarterback and receiver need to build chemistry], but obviously you want as many reps as you can going into a season," said Groh.

"It may take less time with really good players. They just kind of have a feel for each other. One thing that has helped Alshon be a productive player is I think his body language is very easy to read and judge for quarterbacks. When he and Carson get out here and Carson starts learning the body language and where he likes the ball, with the accuracy Carson throws with, I think it'll work out well."