After picking up three more wins at their home away from home, the Washington Nationals are back in the nation's capital for the next 10 games with a chance to pad the largest division lead in the NL.
Their next opponent doesn't have the luxury of a similar cushion.
Washington (66-53) saw its East lead over the Braves slip to 3 1/2 games after dropping two of three in Atlanta last weekend, but it's up to a season-high six after another successful trip to Queens. The Nationals finished off a three-game sweep of the Mets on Thursday with a 4-1 victory, as two-run homers by Adam LaRoche and Bryce Harper led them to an 11th straight win at Citi Field.
''We played really well here,'' manager Matt Williams said. ''Now we've got to go do it at home.''
The Pirates (64-57) were within 1 1/2 games of Milwaukee in the Central and held the NL's top wild-card spot after beating Detroit at home Monday and Tuesday, but dropped two at Comerica Park and fell 2 1/2 behind the Brewers after Thursday's 5-2 loss.
Pittsburgh is currently second in the wild-card standings, a half-game behind St. Louis and a half-game ahead of San Francisco.
There are still injury concerns, though, for a team that plays its next 18 games against NL contenders. Andrew McCutchen (broken rib) and Gerrit Cole (lat) remain on the disabled list and shortstop Jordy Mercer left Thursday's loss with right forearm tightness.
The Pirates hope to get back the other half of their middle infield Friday. Walker has missed 12 of Pittsburgh's last 13 games with lower-back tightness, but was in the on-deck circle Thursday as the final out was made.
"We felt he was a usable player off the bench (Thursday)," manager Clint Hurdle told MLB's official website. "We're optimistic he might be a little more than that (Friday)."
The Pirates could use all the offensive help they can get against Tanner Roark (11-7, 2.86 ERA), who has completed exactly seven innings and allowed one run in five of his last six starts. The right-hander's 2.42 ERA since June is seventh-best in the NL.
This will be his first look at Pittsburgh as he was the Nationals' lone starter not to pitch when the Pirates won three of four at PNC Park in late May.
Charlie Morton (5-11, 3.62) earned his first victory of the season in that series, allowing a run over 5 2-3 innings in a 4-3 win May 23. The right-hander put 10 runners on and wiggled out of numerous jams, but avoided the big inning that has plagued him throughout 2014.
He wasn't so fortunate Sunday against San Diego. Perfect through three innings and up 2-1 after four, Morton gave up four runs in the fifth of Pittsburgh's 8-2 loss.
That marked the 12th time Morton has given up at least three runs in an inning this season, the second-most in the NL behind Philadelphia's A.J. Burnett.
''It was almost like two outings for him,'' Hurdle said. ''One through three and then four and five. It's just two different sides of it.''
LaRoche has been on both sides of this matchup, and he's fared quite well since leaving Pittsburgh. The first baseman has a 1.147 OPS against the Pirates since 2010 - he's 3 for 5 with a homer against Morton - and has gone deep four times in his last eight games overall.
Right fielder Jayson Werth won't start until at least Saturday due to his inflamed right shoulder, but could pinch hit Friday.