Veteran Canadian midfielder Diana Matheson is facing another lengthy absence due to a knee injury.
Seattle Reign FC, who acquired Matheson in a January trade with the Washington Spirit, said the 32-year-old from Oakville, Ont., will miss the 2017 NWSL season after tearing the anterior cruciate ligament in her left knee while training with the Canadian national team.
Matheson, who has won 191 caps for Canada, was scheduled for surgery on Wednesday.
"Earlier (in February) an MRI revealed I had re-torn my previously repaired ACL," Matheson said in a statement. "After careful consideration, and consultations with doctors and staff, I'm moving ahead with surgery to repair it. It's obviously disappointing to be off the field for both Canada and Seattle for this upcoming season, but this will hopefully give me the best chance to be back to where I want to be for both club and country looking ahead to next season, and onward towards 2019 and 2020.
"Unlike my previous surgery, I have the benefit of time for this recovery, and will aim to be back to full speed by this time next year."
Matheson injured the same knee prior to the 2015 World Cup but still made the Canadian roster. She was an unused substitute for the first four games before starting the quarter-final loss against England.
Matheson had knee surgery to repair torn cartilage in her right knee in November 2011. The recovery time was longer than expected but she recovered to play in the 2012 Olympics, scoring the stoppage-time goal that beat France in the bronze-medal match.
The extent of Matheson's most recent injury has been unclear in recent weeks.
She was called up to a January national team camp but did not see action in the so-called Olympic celebration match against Mexico on Feb. 4. Coach John Herdman said at the time that keeping her out was "precautionary" and that team medical staff was assessing her.
When Matheson was subsequently not included on the Algarve Cup roster, Herdman would not provide details on the injury.
"I can't confirm it," he said. "I think that's something Diana would talk to at this point. All I can say is that she won't be selected in the Algarve squad and then we'll assess after Algarve where she's at."
Seattle also did not shed any light, saying only: "Diana is currently under the care of Canada Soccer, and we expect her to be at pre-season training which begins (March 10) in Seattle."
A request for more information from Matheson was subsequently made to the Canadian Soccer Association. The injury was finally detailed in Seattle's release Tuesday.
"I'm so disappointed for Diana — when she told me my heart sank for her," Seattle head coach and GM Laura Harvey said in a statement. "She will be missed this season, but we have built a roster that has huge depth, so the group coming into pre-season will be pushing to show who can step up."
Matheson isn't the only Canadian international to have suffered multiple knee injuries. Goalkeeper Erin McLeod is currently working her way back from knee surgery that kept her out of the Rio Olympics.
The fourth-ranked Canadian women open defence of their Algarve Cup title on Wednesday against No. 15 Denmark in Portugal.