Messi was stretchered off with a knee injury after coming on in the second-half of the 0-0 draw.
"It's a blow, I have been speaking with the doctors. We are waiting for the test and there is nothing else. The estimated time out is not known, depends on the scan," said Vilanova.
"The doctors have been looking at Messi, at first it seems a simple bruise. I would do it again if in the same position. A player can be injured at any time when representing the club.
"Messi was quiet with some concern about the injury.
"It's like any player who is injured. When I see someone from us fall onto the ground I always worry."