"I don't know how they classify it. Not really a seizure but he had some trouble over here," Vikings coach Brad Childress told reporters. "I'd be remiss if I tried to qualify it one way or the other. He seemed like he was stable."
Childress, who is putting the incident in the migraine category, said he recalled a time during Harvin's college career when he was taken to hospital for a similar incident.
The former first-round draft pick was second among all Vikings receivers with 60 receptions and 790 yards in his rookie campaign last season. He was third on the team with eight touchdowns.
"Percy appreciates everyone's concern," said Childress. "He is alert and resting comfortably, but will remain in the hospital overnight."
(Writing by Frank Pingue in Toronto; Editing by Pritha Sarkar/Ian Ransom)