Shapovalov, 17, handed Britain the Davis Cup tie when he was disqualified against Kyle Edmund on Sunday for bashing the ball in frustration and inadvertently catching Gabas in the eye.
Gabas was taken to hospital in Ottawa as a precaution after being left with bruising and swelling around his left eye.
No serious damage was found, but Gabas insisted the incident could have been a lot worse.
"I came off the court looking like Rocky Balboa," Gabas was quoted as saying by Sky Sports.
"The video is quite shocking to look at. We have to avoid some balls during the season but this one I had no chance.
"I feel quite lucky it wasn't worse. Players can be a bit crazy these days.
