Reid was uncertain of Vick's status for Sunday's game against the Washington Redskins but emphasized that the four-time Pro Bowler would remain Philadelphia's starting quarterback when healthy.
"He was a little foggy last night," Reid said Monday. "Mike has a headache is what he's got -- a pretty good one. He's tired. One of the things that is important is that he gets rest."
Vick suffered the injury early in the second quarter of Sunday's 38-23 loss to the Dallas Cowboys and was replaced by rookie Nick Foles, who received a big ovation at Lincoln Financial Field when he entered the contest.
Reid claimed he is "confident" that Foles, a third-round draft selection, will handle the offense if Vick is unable to play against the Redskins.
"Michael is the quarterback," Reid said. "At the same time, I'm confident that Nick will do a good job if given the opportunity."
Vick, who was hit hard on consecutive plays in the second quarter, did not talk to reporters after the loss to the Cowboys. Reid said that the 32-year-old is resting but acknowledged that he likely would not be available for Wednesday's practice.
"He's resting," Reid said. "It's very important he does rest. We're in communication until further testing takes place."
Foles, who passed for 219 yards with one touchdown and one interception against Dallas, will receive all of the snaps with Philadelphia's first-team offense Wednesday. Reid said Trent Edwards will be the second-team quarterback.
"If (Foles) gets an opportunity to start, I'll be excited to see him play," Reid said.
Information from The Associated Press was used in this report.