Whitecaps coach Martin Rennie said Mattocks underwent arthroscopic knee surgery Thursday. The coach said the team does not put a time frame on recoveries, but he does not expect the Jamaican international to be out too long.
"He'll be frustrated, but it's not a major injury," said Rennie on Friday. "He just had his knee cleaned up a little bit. So it shouldn't set him back too much."
Mattocks has struggled in his second Major League Soccer season after shining as a rookie. He has started just six of the 13 games in which he has appeared, recording three goals and one assist.
The 22-year-old did not travel to Vancouver's last game in Los Angeles due to the knee injury.
Mattocks' knee started bothering him in the warmup before Vancouver's game against Chicago two weeks ago, but he still came on as a substitute in the final two minutes.
Then it swelled up while he was en route to play for the Whitecaps reserve team against Real Salt Lake, said Rennie.
Mattocks tested the knee in a couple of training sessions afterwards, and the club felt it should be cleaned up through surgery.