Minnesota United will return to Major League Soccer play at 7 p.m. Wednesday against the Houston Dynamo at TCF Bank Stadium, but injury concerns still plague the Loons.

Center-back Brent Kallman is still technically day-to-day with an MCL sprain he endured in a match against the Vancouver Whitecaps FC on June 24. But coach Adrian Heath said Kallman feels "OK" and very well might have to play this Wednesday, given the Loons' situation.

With Francisco Calvo and Jermaine Taylor both still gone on national team duty for the CONCACAF Gold Cup (midfielder Johan Venegas as well), Kallman injured and Vadim Demidov unable to break into the squad, United has just Joe Greenspan and new signing Michael Boxall as true center-backs. But Boxall, along with winger Sam Nicholson, is still not yet cleared to play with his visa and international transfer certificate still pending. Heath said it could possibly be as late as Wednesday before the team finds out if Boxall and Nicholson can play.

Starting midfielder Kevin Molino also rolled his ankle and is day-to-day for the Loons, Heath said.

While the injuries and national team call-ups continue to hinder the side, United is still trying to make moves during this secondary transfer window, which closes Aug. 9. Heath said the team is in negotiations with two to three more players, one from inside the league the rest from outside. The goal is to sign four to six new players, Heath said. United already has three in Nicholson, Boxall and forward Brandon Allen.