Kelly, who typically does not reveal much about injuries, said he did not know the results of the MRI that Vick underwent Monday.
Vick's injured hamstring is not as serious as the original strain, league sources told ESPN NFL Insider Ed Werder. Vick will be evaluated weekly.
Kelly said Monday he would proceed as though Vick would not be available for Sunday's game against the Oakland Raiders -- and perhaps longer.
"Mike didn't seem like he was going to be ready this week," Kelly said. "He felt like, the first time, that he was going to be back after the [Oct. 6] Giants game.
"This is the first time I've talked to him where he thought he may be out. We'll see after we sit down and visit, after we get the final [MRI] results."
Kelly said Vick was "day to day" after the original injury. After Vick lasted less than one half upon his return Sunday, Kelly said the original prognosis was for Vick to miss 10 to 14 days.
Rookie Matt Barkley would start if Vick and Foles are unable to play. If that's the case, the Eagles would likely have to add another quarterback this week.
G.J. Kinne is on the practice squad but was signed just last week.
"I wish I knew a lot more than I do know," Kelly said of his quarterback situation. "I don't have the final answer right now."