Struggling Colorado Rapids to face FC Dallas without young guns Shane O'Neill, Marlon Hairston

COMMERCE CITY, Colo. – The Colorado Rapids are in the biggest slump of their season, and they’ll be at least two men short for Saturday’s key Western Conference tilt in Dallas.

Defender Shane O’Neill (knee/groin) and midfielder Marlon Hairston (groin strain) are both unlikely to travel to Texas for Saturday night’s showdown against FC Dallas (9 pm ET; MLS LIVE).

O’Neill’s injury appears to be the more serious of the two. He originally went down with a sprained knee following a blocked shot in a match on July 4, but now he’s battling an apparent groin injury that may keep him out indefinitely.

“They’re treating his groin,” head coach Pablo Mastroeni told MLSsoccer.com on Wednesday of O’Neill. “I have no idea where he’s at as far as availability.”

Hairston, meanwhile, suffered his own groin injury during warmups prior to the Rapids’ 1-0 loss to Real Salt Lake at Dick’s Sporting Goods Park last Saturday night, forcing him to miss a United States U-23 camp in the Bahamas this week.

“I don’t want to rush anybody for any reason,” Mastroeni said. “It’s better to make sure you’re healthy and 100 percent before you step in.”

Marvell Wynne will step in at center back once again in O'Neill's absence, while Jose Mari's return to action helps mitigate Hairston's loss, but it’s still not an easy draw this weekend for the Rapids. They’ve won just one of their past seven games and they’ve allowed 19 goals in 10 games on the road this season (2-3-5).

Still, Mastroeni said this week that despite the team’s loss to RSL last time out, he’s optimistic about the way the team is playing.

“I saw probably the best defensive performance I’ve seen in Major League Soccer [from the Rapids in the 1-0 loss to RSL on Saturday] since I’ve been playing,” Mastroeni told reporters on Wednesday. “I feel with the way we’re playing in spurts, now, why can’t put a whole game together at times? Experience. We haven’t been there before.”

Chris Bianchi covers the Colorado Rapids for MLSsoccer.com.