Andreas Ivanschitz - Seattle Sounders - holding head with back to camera

The Seattle Sounders will be without midfielder Andreas Ivanschitz for their next match, and possibly the last two of the regular season.

The Seattle Times' Matt Pentz reported on Thursday that Ivanschitz, one of the club's creative keys, has a right knee sprain that will keep him out of Sunday's match at Supporters' Shield-leading FC Dallas (5 pm ET; MLS LIVE) and could cause him to miss the regular-season finale against Real Salt Lake on Oct. 23.

Interim coach Brian Schmetzer called the Austrian midfielder, who has three goals this season and shares the team lead with eight assists, "probably doubtful" for the RSL match.

Ivanschitz was injured early in Wednesday night's match against Houston, and his absence was evident as the Sounders had to settle for a scoreless draw with the last-place Dynamo. An MRI exam on Thursday revealed the extent of his injury.

“It’s not easy to replace a guy like Andreas,” veteran Sounders forward Herculez Gomez said afterward. “He oozes quality.”

Seattle will also be without defensive midfielder Osvaldo Alonso on Sunday because of a red-card suspension, and forward Clint Dempsey is out for the rest of the season with an irregular heartbeat. The Sounders are currently fourth in the Western Conference, but just four points ahead of seventh-place Portland with two matches to go.