[MLS] Though it held Houston goalless last week in the first leg of their Western Conference semifinal series, Seattle might be tweaking its back line for game two. Veteran defender Tyrone Marshall, who played 26 games (25 starts) for the Sounders during the regular season, didn't play against the Dynamo. During pre-game warm-ups at Qwest Field Thursday, Marshall felt tightness and instability in his right knee. He informed Coach Sigi Schmid, who decided to pull him from the lineup in favor of former Dynamo defender Pat Ianni.

An examination revealed a lateral collateral ligament sprain in the knee, which he'd suffered the day before the match during training when he got caught in a goalmouth tangle. He did some light jogging Monday and hopes he can get in a full training session Thursday in preparation for the second match Sunday in Houston.

"Yesterday I could hardly walk and today I was jogging, so that's progress," said Marshall to mlsnet.com on Monday. He has played 21 postseason matches, including the 2002 and 2005 MLS Cups for the Galaxy, both of which they won, and turns 35 next week.

Ianni got the start Thursday alongside central defender Jhon Kennedy Hurtado and nearly replicated his feat of scoring against the Dynamo during the regular season. He hit the crossbar with one header and another was cleared from under the bar by Dynamo midfielder Brian Mullan.

Schmid says he won't decide until the end of the week who will be paired with Hurtado in the middle. Ianni, 24, was acquired from Houston last January and played 17 matches (10 starts) in the regular season. The Dynamo and Sounders tied for the best defensive record during the regular season by conceding 29 goals in 30 matches.

"I'm hoping, cross my fingers, that I'm healthy and able to go in there and add that experience so we can move on to the next stage," Marshall said.