While the Washington Nationals have yet to lose on what figured to be a daunting road trip, the Kansas City Royals' offensive struggles continue to highlight their current rough stretch.

With Tanner Roark trying to extend his 15-inning scoreless streak, the Nationals look to stay undefeated at the halfway point of their 10-game trek Tuesday night against the reeling Royals.

Washington (18-7) totaled three runs while being swept by Philadelphia in a three-game set before embarking on this trip. The Nationals scored 17 times in sweeping the first stop for three in St. Louis, then managed enough runs in Monday's 2-0 win at Kansas City (13-12).

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''It usually takes you a little while to get going,'' said Washington manager Dusty Baker, whose team concludes the trip with four at Wrigley Field.

"We have to keep rolling."

Washington's offense came in the first inning on a RBI double from Ryan Zimmerman and a run-scoring groundout by Daniel Murphy. Bryce Harper snapped an 0-for-16 slump with a single in the sixth, then was thrown out trying to steal.

Murphy, who recorded his 1,000th hit, is among the major league leaders with a .382 average. He had three hits Monday after going 3 for 20 with seven strikeouts against the Royals in the World Series for the New York Mets.

Roark (2-2, 2.03 ERA) has not allowed a run in three of his five starts, including the last two during which he's given up two hits over seven innings in each.

"I was using all four pitches on righties and lefties, keeping them off balance," Roark told MLB's official website after receiving a no-decision in Thursday's 3-0 loss to Philadelphia.

"That's the name of the game."

Making his first start against the Royals, the right-hander is 2-0 with a 1.89 ERA in his last three interleague starts.

None of that would seem to bode well for Kansas City, which has been blanked in three of four games and totaled 11 runs while going 7 of 49 with runners in scoring position to lose six of the last seven.

''We're not firing on all cylinders offensively,'' manager Ned Yost said. ''We've got guys that are struggling right now, guys that are proven players, guys that have tremendous track records and they're going to break out of it here real soon.''

Alex Gordon is mired in a 1-for-15 slump over five games. Salvador Perez is 2 for 18 in his last five.

Eric Hosmer, however, is batting .358 while hitting safely in 20 of 21 contests.

"We've been up and down," Hosmer said. "We've still got some guys who haven't got hot yet. Once those guys get hot, we know how tough we can be. We're not worried."

For the fourth time this season, Kansas City's Chris Young (1-4, 6.12) failed to complete six innings Wednesday. He lasted 5 1/3 and all three runs he allowed came on two homers in a 4-2 loss to the Los Angeles Angels.

The right-hander has yielded six home runs in 25-plus innings.

''Physically, I felt great," Young said after his latest outing. "I felt like I pitched better than my results."

Young, who turns 37 later this month, last faced the Nationals in July 2012.

Harper is 4 for 8 with a homer against him.