Late in Friday's scoreless tie with Real Salt Lake, the Argentine veteran limped off the field with a hamstring injury. MRI results have Sounders coach Sigi Schmid cautiously optimistic that Rosales might be available Thursday night in Utah.
"Mauro went through the early part of the warmup today and then we sent him in with the trainers," Schmid said. "It was definite progress from yesterday. They've been able to localize the injury. We'll see how he feels tomorrow and day by day."
Seattle should have leading scorer Eddie Johnson back in the starting 11 for this crucial match. Johnson was held out of the first contest after tweaking his hamstring in the regular-season finale.
The Sounders have yet to score a goal against RSL in four meetings this season. They had several fantastic chances last Friday but were turned away by some incredible work by keeper Nick Rimando.
Players' health and fitness are factors when Schmid creates his final lineup, especially knowing the match could go into overtime or even penalty kicks.
"You have to think about starting people who have the capability of going 90-plus minutes," Schmid said. "If you don't you're locked into some subs, and if someone is injured you're in some trouble."
First kick has been moved to 7 p.m. for national television. Ross Fletcher and Kasey Keller will call the action on KIRO Radio 97.3 FM.