Tanner Roark will take a four-game winning streak to the mound when the Nationals host the Orioles in a makeup game on Monday night.
The two sides were rained out at Nationals Park on July 8.
Roark is 8-2 with a 2.20 ERA in his last 10 starts, and during the course of his win streak, he's been even better. The 27-year-old righty allowed one run over seven innings for the fourth straight start on Wednesday against the Marlins, giving him a 4-1 record with a 2.06 ERA in July for the National League East-leading Nats.
"Tanner continues to pitch well for us," Nationals manager Matt Williams said after Roark improved to 11-6.
The American League East-leading Orioles, meanwhile, will counter with Kevin Gausman as they begin a short four-game road trip.
The 23-year-old watched an early no-hit bid get derailed against the Angels, but he managed to go seven innings and turn in a quality start as he battled Los Angeles starter Garrett Richards in a pitchers' duel on Wednesday.
"Two good guys, two good-looking pitchers," O's manager Buck Showalter said of the Gausman-Richards matchup. "You're trying to win a game, but you're also a fan of the game and you see two guys like that pitching, and you say, ['Wow']. I wouldn't say 'fun,' but it's entertaining to watch. It's not entertaining to hit."
Gausman will make his 11th start of the season and fifth on the road. He's 1-1 with a 2.86 ERA away from Camden Yards. He's made one career start against Washington, taking the loss over four innings on May 28, 2013, in his second big league start.
Nationals: Harper sits while Hairston gets rare start
Bryce Harper was not in the starting lineup on Sunday against Phillies left-hander Cole Hamels. Scott Hairston got the start in left field instead, and Harper struck out after replacing Hairston in the field in the eighth inning.
Harper has been occasionally tweaking his batting stance while trying to find some answers at the plate.
Harper missed 57 games after injuring his thumb on April 25 and subsequently having surgery, and he's been inconsistent on offense. He posted a .228 batting average in July, and he is batting .260 with three homers in 50 games.
Orioles: Jimenez set to rejoin team
Injured right-hander Ubaldo Jimenez will rejoin the team Monday, Showalter said on Sunday.
Jimenez, who's on the DL with a right ankle sprain, was set to rejoin the Orioles in Washington before traveling north for the series against the Blue Jays.
"He's champing at the bit to get back. You can tell," Showalter said.
Jimenez -- 3-8 with a 4.52 ERA in 18 starts this season -- was sent on a Class A rehab assignment on July 29. The 30-year-old was acquired by Baltimore as a free agent in February.
• The Orioles ranked fourth in the Majors with a 2.96 ERA in July, their best monthly mark this season.
• Nationals leadoff man Denard Span has reached base safely via hit or walk in 29 straight games dating to June 28.
Jamie Ross is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.