Eagles wide receiver DeSean Jackson suffered a concussion and Falcons cornerback Dunta Robinson injured his head in a nasty head-on collision during the second quarter of Atlanta's 31-17 loss.
"He's in the training room today. Up moving around, in good spirits," Reid told reporters on Monday. "I'll tell you, it would be a real stretch for him to make it this weekend."
Falcons coach Mike Smith was unsure about Robinson's timeframe on Sunday.
"He seems to be fine," Smith said of the cornerback whom Atlanta signed as a free agent during the offseason. "It was a very violent collision. I saw him and knew he couldn't return, and that's all I really know."
The same cannot be said for Jackson. NFL Network and FOX Sports' Jay Glazer reports Jackson has a "severe concussion" and suffered memory loss from the hit.
Last year, a concussion caused Jackson to miss one game. This year, Jackson could be out of action even longer.
His status moving forward isn't known. He won't be able to play until he's cleared by a team doctor and an independent neurological consultant.
Both players stayed on the turf for several minutes before being helped from the field. Jackson dropped a pass when hit by Robinson, who led with his head and hit the receiver in the helmet. Robinson was flagged for hitting a defenseless receiver.
"That was scary," Eagles wide receiver Jeremy Maclin said.
Eagles quarterback Kevin Kolb, who was sidelined by a concussion after starting the season opener, was asked what he would tell Jackson.
"Take it seriously because it is serious," said Kolb, who returned to practice before the Eagles' third game but didn't get back on the field until Michael Vick was injured two weeks ago during a loss to the Washington Redskins. "I just felt so bad. I'm part of the play, and I never saw the guy.
"DeSean is a tough guy, and he'll be out there as soon as he can. We got to take this concussion situation serious."
Eagles owner Jeffey Lurie said after the game that the league should take a tougher stance on helmet-to-helmet hits, including stiffer penalties.
"It's not something that should be in the game. It should be legislated out of the game," Lurie told USA Today.
Lurie said he didn't think Robinson intended to knock Jackson out of the game, but said the league should discourage that from happening.
"I doubt that happened in this case," Lurie said. "But going forward, we've got to protect players and penalize players who issue concussions.
"Every offseason we've got to make it the highest priority and we do. It's just, 'How far do we go?' We've got to go even further than we have."
The Associated Press contributed to this report.
