"It helps when you're out there together, no doubt," Cooper said. "When you're with somebody every single day and practicing with them every single day, you can pick up on things and help each other."
Chip Kelly hasn't left himself open to a lot of second-guessing during what is still a honeymoon period as head coach, but the receiver position holds that possibility if things don't work out for some reason. Releasing DeSean Jackson won't really matter if Cooper and Maclin stay healthy and if rookie Matthews is an effective replacement for Jason Avant in the slot position. It won't matter if veteran Brad Smith and rookie Josh Huff, both of whom are injured at the moment, are able to contribute as well.
But it will be brought up - the hubris of discarding Jackson - if an offense that was ranked among the top 10 in passing yards last season can't replicate that pace with the current receivers. That won't be anything more than an idle concern for a while, and even less so if Maclin, Cooper and Matthews are on the field. Because of Maclin's injury history, his status will draw the most attention and have the coaches watching carefully.
"It felt good to have a chance to run around and run some routes. Training camp's a grind, man. It's like this each and every year," Maclin said. "Coming off knee surgery, my body is just not used to doing that. I'd say that missing two days all of training camp makes me pretty happy."
That's one way to look at it, and it is a lot more important that Maclin's knee is fully recovered than whether he has to deal with a strained hamstring for a little while. The other way is to worry that it's going to be one thing or another all the time.
"Last Tuesday in New England, my knee felt better than it has since surgery," Maclin said. "I think I'm over that point where there are worries [about it]. It looks good to have us all on the field together and playing, but each of us has our own relationship with Nick [Foles] that has been building for years. I don't think it put us behind because we haven't been out there together."
They can catch up some against the Steelers at Lincoln Financial Field on Thursday when the Eagles play the third of their four exhibition games, and by far the most important one.
"Typically, this is the game where the first-line guys play the most," offensive coordinator Pat Shurmur said. "So we'll put some first-line guys out there and give them most of the reps and that's really where we're at right now."
With Maclin, Cooper and Matthews on the field, Foles will have an interesting array of targets to mix and match, along with the tight ends and backs. Cooper is big and strong, Matthews only an inch shorter at 6-foot-3 and very quick, and Maclin is capable of open-field speed. Together, it will look like a group that will test defenses. With a piece or two missing, it will look like a group that could have used Jackson.
"Those three all have a nose for the ball and good special awareness, which is important to this offense. They anticipate and you can hit them on the run and keep them moving," said backup quarterback Mark Sanchez. "You get those guys healthy, and the way our O-line is playing, that's a pretty special group, very talented."
On Monday, the group was out there for the first time and it was a moment to savor for the offense. The Eagles just hope it doesn't become a moment to merely remember.