Washington's Mike Bacsik led the Nats to a 3-0 win on Saturday that dropped Colorado to a 2-1 deficit in the series.
"They've found a way to keep our offense down," second baseman Jamey Carroll said. "They had big hits, and we just didn't get anything going. We really haven't this whole series."
The Nationals are now threatening to spoil what looked to be a successful trip for the Rockies, who can salvage a series split with a victory on Sunday. Colorado had moved into a tie for third in the National League West on Friday, but dropped back to fourth after Saturday's loss.
The loss was the second consecutive time that a strong outing from Rodrigo Lopez did not end in victory. Lopez pitched into the seventh inning of the game, then was removed for Jeremy Affeldt with no outs and two runners on.
Before that, Lopez's lone blemish was a home run given up to Felipe Lopez in the sixth inning. Last Saturday in Milwaukee, Lopez pitched a one-hitter, yet still lost.
"He's made two good outings," manager Clint Hurdle said. "He pitched very well in the seventh inning, his ball just got up. If he gets out of the seventh inning, he gets out with one run."
Lopez said his mechanics have been much smoother since the All-Star break, and the timing on his arm movements is better. He added that he was unable to get the ball down in the seventh inning, resulting in the two baserunners.
Affeldt came on in relief, and with two outs and runners on second and third, the Nationals brought in All-Star Dmitri Young to pinch-hit. Young had been sitting out the game with an injured heel, but Affeldt didn't want to take his chances, and intentionally walked Young to load the bases.
The next batter was pinch hitter Tony Batista, who drilled a single into the left field and drove in two runs.
"He just didn't make a pitch," Hurdle said. "It was a slow curveball that ended up over the middle of the plate."
Affeldt has struggled recently, which has been uncharacteristic of his performances this season. In his last four outings, he's allowed four runs. He wasn't charged with any on Saturday, but two runs scored while he was on the mound.
"That's two times in a row now they've beat me on that pitch," Affeldt said. "It's just one of those times for me that's kind of hit or miss. I've just got to keep balls down in the zone and they will eventually start going my way instead of their way."
The Rockies' offense started out strong, with a pair of singles to open the game. A double play squashed that, though, and the team didn't get another hit until a single in the third inning.
Those three singles, combined with two walks, provided the only baserunners of the day for the Rockies. Hurdle credited a strong outing from Bacsik, who went 6 2/3 innings and allowed three hits.
"He changed speeds very effectively and really controlled our bat speed," the manager said. "Also, their bullpen has been very effective."
The Rockies fell to 5-4 on the road trip, including a sweep in Pittsburgh. The team will return home still in contention, which is an improvement over last season, when it went 2-8 on a similar road swing after the All-Star break.
"We were really starting to spiral at this time last year," Hurdle said. "Now we're holding our own. We expect to come in here, take the last game, and head home."
Michael Phillips is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.