Minnesota United left-back Marc Burch, who met with a specialist in Philadelphia on Monday, underwent successful bi-lateral sports hernia surgery Tuesday morning, the team said. He will likely be out for eight to 12 weeks.

While coach Adrian Heath said he was hopeful for a return in possibly six weeks, it just depends on how the recovery goes.

Burch's groin injury has plagued him all season, but he had managed to play through it until now. He started and played nine matches, totaling 783 minutes, for United this season since he came to the Loons in a March trade with the Colorado Rapids.

With the starter out this past weekend against Salt Lake, right-back Jerome Thiesson switched to Burch's spot on the left and Kevin Venegas filled in at Thiesson's usual spot. Heath said Monday he'd prefer to play Thiesson in his natural position, which could mean left-back Justin Davis might have a shot at playing 7 p.m. Wednesday against the Portland Timbers at TCF Bank Stadium.

With Burch unavailable until possibly mid-August or mid-September -- a large chunk of the remaining season -- Heath said that might put a new emphasis on the upcoming transfer window, which opens July 10.

"We realize that we've got to bring reinforcements in, and I think that if we could bring one in in all sorts of areas, defending, midfield and attack, then we probably would like to," Heath said. "But we're actively looking at players in a few positions."

Heath said the Loons could be looking at three to four moves during that window.

"We'll probably start to hear a lot more internal stuff within the league in the next week or so, 10 days," the coach said. "We're getting to that stage now where people are really looking for that next window, and if they're bringing people in from abroad, they might have to move people out from their own roster. So we might be in the same boat. But I'm really optimistic that we ... down the road, there's going to be new additions to our team."

In addition to Burch, Heath said midfielder Johan Venegas is still not fully recovered from his sciatic pain that also kept him out of this past weekend's match. Midfielder Ish Jome also picked up an ankle injury Monday.