BOYDS, Md. -- D.C. United booked a place in the U.S. Open Cup final with a gritty win over a tenacious Rochester Rhinos side on Tuesday night, yet the capital club's celebrations were decidedly muted after two grisly injuries draped a pall over the Maryland SoccerPlex.The match itself was a compelling, tightly-contested affair. The home side grabbed a first-half lead on a Jaime Moreno penalty kick only to be pegged back by Tai Atieno's 68th-minute leveler, setting the stage for Boyzzz Khumalo to deliver a timely game-winner eight minutes from full time.But Rhinos midfielder Darren Kenton suffered a serious ankle injury just moments after his team's goal and Khumalo broke his wrist in the dying minutes, prompting fright and concern on all sides."For me, the game's overshadowed by a couple injuries, one to them and one to us," said D.C. head coach Tom Soehn, "and that's disappointing, because everybody worked hard and you just never want to see any injuries, period."Kenton looked to have been injured by a full-blooded slide tackle from United midfielder John DiRaimondo, who had just entered the match, and after the match Rhinos coach Darren Tilley expressed his displeasure with the challenge. Referee Abbey Okulaja was close to the play and did not call a foul, however, and photos subsequently suggested that the Englishman had rolled his ankle on the wet turf an instant before DiRaimondo's arrival."It was a fair challenge -- John went in hard and I think the challenge was fair," said Soehn. "Unfortunately the result wasn't good. So there was no egregiousness on John's part -- he was out to win the ball."Later on, Khumalo would prove to be the man on the spot as he slotted home an opportunistic winner after Rochester goalkeeper Tim Melia denied Chris Pontius on a breakaway. But the South African's evening would conclude at a local hospital after a Melia clearance cannoned into his wrist in injury time.Nonetheless, he was all smiles despite the sling on his right forearm as he explained to reporters that his scoring contribution was the payback for his glaring miss in the first half of United's 3-1 win against Colorado on Saturday."I'm so excited because if you realize, last week I missed a goal, an open chance, so this was a makeup for it," said Khumalo, before describing the play that led to his injury."The 'keeper was clearing the ball and my wrist was out of position, I guess. The ball hit my wrist and when it came up, I just looked at my wrist and I just got on the ground -- I called [trainer] Peter [Calabrese] up because it was broken."His coach and teammates offered up warm praise for Khumalo's workmanlike performance over the 90 minutes, as he covered plenty of ground and gamely ranged from wing to wing while United labored to break down Rochester's stubborn defensive scheme."Boyzzz put a lot of work in and for him to end with an injury like that, it's disappointing," said Soehn. "He came up with a big play. He followed up Chris' shot and a lot of guys wouldn't do that. So you credit him for scoring a big goal for us."Tuesday marked the third consecutive round of Open Cup play in which United struggled to dispatch lower-tier opposition, but the Black-and-Red were content to escape with a result that enables them to defend the Dewar Trophy at their RFK Stadium home in September. D.C. also hosted the 2008 Open Cup final."It's always a battle with teams that come from the second division," said Moreno. "They put in a great performance - we knew that their strength is the long balls, a very English style and we knew that -- but we tried to break them down the way they were prepared, the middle, which was a mistake for us."But at the end of the day we got the three points. We got the win."