Maclin suffered a hip pointer in the season-opening win over the Cleveland Browns, but was still able to start in the Eagles' Week 2 win over the Baltimore Ravens. He scored a touchdown but needed to leave the game when he suffered another hip pointer in the same spot.
After Sunday's game, Maclin said the latest injury hurt more than the previous one.
He had been trying throughout the week to return to the field and was even a limited participant in Thursday's practice before the Eagles declared him out.
"We're going to give him the week off," Reid said.
Eagles quarterback Michael Vick spoke to Maclin and told his receiver that he just wants him to get healthy. Maclin will stay behind in Philadelphia to continue rehabbing, and Reid does not anticipate the injury lingering to the point that it puts next week's game against the New York Giants in doubt.
"He wants to be out here," Vick said. "He wants to be a part of this game this weekend, but his body is not allowing him to do it."
The onus will be on Vick to involve the other receivers. Jackson will likely receive heavy coverage from Arizona's defense, so the Eagles need to establish secondary targets. Celek is reliable, and Harbor should see a larger role, too, but Avant and Johnson will be the primary beneficiaries of Maclin's absence.
It's not unfamiliar territory for Avant, who has 34 career starts and helped fill the void when Maclin missed time last season. But Avant is most valuable to the Eagles playing in the slot, and his role is different if he is pressed into playing outside. Avant noted that the change is in the coverages he sees and how he must watch film.
Avant compared the Eagles' current plight to what the Giants endured Thursday, when Hakeem Nicks and Domenik Hixon missed New York's 36-7 win over Carolina. Reserve wide receiver Ramses Barden had 138 yards in a more prominent role, and the Giants' offense still thrived.
The player to watch Sunday will be Johnson, the 5-foot-8, 175-pound undrafted rookie. Johnson plays in the spots that Maclin occupies, so he likely will receive more opportunities. When Maclin exited the game in the third quarter last week, Johnson received steady playing time.
"It helped, definitely," Johnson said. "Experience always helps. Just going out there and getting a lot of plays, a lot of reps, just getting used to the game speed - it helps me. It's going carry over into this week."
When the Eagles lost to the Cardinals in Philadelphia last season, Jackson was benched, Vick suffered an injury early in the game, and the undermanned Eagles offense struggled.
Maclin is a key member of the Birds offense, and he and Jackson give the Eagles one of the best receiving tandems in the NFL. Without one of them, the offense is not the same.
"We want to see Jeremy back," Avant said. "But we know we have capable guys, guys who are willing to go out and prepare hard and make the best of their opportunity."
Contact Zach Berman at email@example.com, or follow on Twitter @ZBerm.