PITTSBURGH -- Hot-hitting James Harrison singled in the winning run in the two-run seventh inning as the Pittsburgh Pirates rallied to beat the Washington Nationals and ace Stephen Strasburg 3-2 on Saturday night.

The Nationals led 2-1 when catcher Russell Martin led off with a single and took third on left fielder Starling Marte's two-out single. Pinch-hitter Jose Tabata tied it with a sacrifice fly.

Nationals first-year manager Matt Williams decided to intentionally walk left-handed pinch-hitter Travis Snider, although he was hitting just .214, to get a right-right matchup with Strasburg (3-4) against Harrison, a utility player who has taken over as the regular right fielder in the last week with Tabata and Snider both slumping.

Harrison grounded a single up the middle that scored Marte with the go-ahead run and is hitting .328 in his last 24 games.

The Pirates won their fourth consecutive games and the Nationals dropped their fourth straight and fell below .500 for the first time this season at 24-25.

Jared Hughes (3-1) pitched one perfect inning for the win and Mark Melancon worked a 1-2-3 ninth for his ninth save of the season.

Strasburg gave up three runs and seven hits in seven innings with two walks and seven strikeouts. He had his seventh consecutive quality start but fell to 0-3 in five road starts.

Pirates starter Gerrit Cole went six innings and allowed two runs, five hits and three walks while striking out seven. He has struck out at least six in seven of his 10 starts this year.

Strasburg was the first overall pick in the 2009 amateur draft and Cole was the top pick in 2011, marking the first time two No. 1 overall picks started against each other since Aug. 21, 2012, when the Kansas City Royals' Luke Hochevar faced the Rays' David Price at Tampa Bay.

The last National League game to feature two No. 1s came on May 16, 2005, when the Mets' Kris Benson and the Cincinnati Reds' Paul Wilson squared off in New York.

Martin and Marte had two hits for the Pirates and second baseman Neil Walker homered.

First baseman Greg Dobbs had two hits and shortstop Ian Desmond hit a home run for the Nationals, who have scored just seven runs during their four-game skid, going 2-for-27 with runners in scoring position and leaving 35 runners on base.

The Nationals are 20-1 when they scored at least four runs but 4-24 when they don't.

Both teams traded one-out solo home runs in the top of the inning to open the scoring.

Desmond hit a drive into the left-field bleachers for his ninth homer of the season. Walker countered with his 10th, which landed in the Nationals' bullpen in center field.

Catcher Wilson Ramos put Washington ahead 2-1 when he dropped an RBI single into right field with two outs in the bottom of the fifth.

NOTES: Washington 1B Adam LaRoche is expected to be activated from the 15-day disabled list Sunday for the finale of the four-game series. He has been out since May 10 with a strained right quadriceps. ... Nationals LHP Gio Gonzalez reported no problems Saturday after playing catch for the first time since being placed on the disabled list last Sunday with left shoulder inflammation. He was originally supposed to throw Friday, but that was postponed when he felt stiffness in the shoulder. ... Pittsburgh manager Clint Hurdle was not ready to commit to RHP Jason Grilli as the full-time closer, though he pitched a scoreless ninth inning on Friday night for the save in his first appearance since April 20, the day before he went on the DL with a strained left oblique. ... Pirates INF Clint Barmes started in place of SS Jordy Mercer for a second straight game, a day after stealing his first base since 2011. ... Washington RHP Doug Fister (1-1, 3.93 ERA) faces Pittsburgh LHP Francisco Liriano (0-4, 4.86) on Sunday.