SEATTLE -- Seattle Storm guard Sue Bird needs arthroscopic surgery on her left knee and will be out indefinitely, another big blow for the defending WNBA champs.

The Storm said Tuesday that the 11-time All-Star has a loose body in her knee. Bird said it's something doctors have noticed in the past but that never affected her on the court until she started to get ready for the upcoming season, when she noticed she was having trouble sprinting and jumping.

Bird will undergo surgery in Connecticut in the near future and will return to Seattle for rehab. She said there is no estimate on when she can return, but The Seattle Times reported that she is expected to miss eight to 10 weeks. The Storm open the season hosting Phoenix on Saturday.

"I've been here before so I guess that is a good thing. I know what to expect and how to approach it," Bird said. "I've already gone through the roller coaster of emotions because just getting to the point of knowing I had to have surgery took a lot doctors and a lot of MRIs and things like that. In some bizarre way it's nice to know what the plan is and you can kind of wrap your head around that. You can have your down moment but then kind of be like, `OK, this is how we're going to move forward.' So that's where I am."

The news about Bird is the third significant setback for Seattle in recent weeks. Reigning league MVP Breanna Stewart is out for the season after tearing her Achilles tendon playing overseas. The status of head coach Dan Hughes is uncertain. He underwent surgery to remove a cancerous tumor in his digestive tract.

Bird did not play in either of Seattle's preseason games.

"The most important thing to us is that Sue is healthy and strong. Based on her feedback and evaluation from her longtime surgeon and our medical team, it was determined the best course of action was a scope," Storm CEO and general manager Alisha Valavanis said. "We have confidence this will support Sue's full recovery and we look forward to her return to the court."

This will be the second time in her Seattle career Bird has been sidelined by knee problems for most, if not all, of a WNBA season. She missed the 2013 season after undergoing surgery to remove a cyst from her left knee.

Bird won her third WNBA title last season at age 37 after helping Seattle to a three-game sweep of Washington in the league finals. But it was Game 5 of the Western Conference finals that will be remembered as perhaps Bird's best game as a professional. She scored 14 of her 22 points in the fourth quarter as Seattle rallied to oust Phoenix.

"It happened so recently you don't want to get too high on something that was recent, but when it's all said and done I'm pretty sure that will be the defining moment of my career," Bird said recently, prior to news of her knee problem.

Bird averaged 10.1 points and a career-high 7.1 assists per game last season, while also shooting a career-best 46.6% from the field and 44.8% on 3s. Her absence is going to put more on the plate of second-year guard Jordin Canada and Jewell Loyd. Bird and Stewart contributed an average of 32 points per game combined last season for the Storm.

"This is my opportunity to step up and have a big role and lead my team," Canada said. "That's all I'm focused on."

The Associated Press contributed to this report.