The road in recent starts has been kind to Nationals left-hander John Lannan. He entered tonight’s game 5-0 with a 3.15 ERA away from Nationals Park over his past six outings, and a rain postponement on Friday allowed him to get his customary rest for this final game of the three-game series.

Lannan looked road-ready again in the early going, allowing one base runner through the first three innings. Even then, he wound up facing the minimum thanks to a first-inning double play that erased Andrew McCutchen’s single to lead off the bottom of the first.

But the weather and a fielding gaffe in part conspired in Lannan’s undoing in the fourth, where he labored through eight hitters and allowed all four of his earned runs. Pittsburgh scored its first run when right fielder Jayson Werth’s throw to the left of home was off line and got by catcher Wilson Ramos, allowing Jose Tabata to score from first on what was ruled Neil Walker’s single and an error.

Then it didn’t help that home plate umpire Phil Cuzzi stopped play with two outs and Lannan ahead of first baseman Steve Pearce, 0-1, with Walker on third after the Werth miscue.

“The rain, when he called it, it wasn’t that big of a factor,” said Lannan, who fell to 2-2 and raised his ERA to 4.05. “I had just thrown a first-pitch strike to Pearce, and after that I thought I was going to get him, so I was kind of shocked he called it in that situation.”

Lannan walked Pearce after play resumed, and third baseman Brandon Wood cleared the bases with a double to right center for a 3-2 Pirates lead.

Lannan did manage to retire the side in the fifth, including a pair of strikeouts looking, and two more batters in the sixth, extending the Nationals’ run of having all starters pitch at least five innings in each of their 21 games. Washington is the only club to have accomplished that this season, and it is seven games from matching the Nationals’ longest such stretch since relocating to the nation’s capital in 2005.

But after an error by shortstop Ian Desmond put runners on first and second with two out in the sixth, Lannan was done for the night. Reliever Todd Coffey cleaned up the mess by striking out catcher Chris Snyder for the final out.

“I thought John’s pitch to Wood was a pretty good pitch,” Nationals Manager Jim Riggleman said. “I saw a replay of it, and it looked like it was in a decent spot. He’s got good power, and he drove into right center on us.”

While Lannan was slowing down, Pirates starter Paul Maholm was in a groove. The left-hander retired the final 13 batters he faced and allowed jus three base runners after an unsteady first inning, when he yielded both of his earned runs.

Maholm was unaffected by the rain delay, or at least he showed no effects while on the mound. He allowed just one hit over his last six innings, and he struck out six, including three to end innings.

“It’s tough, but you have to deal with it,” Lannan said of the delay. “Maholm had the same conditions. Coming back out there with two outs in the fourth, I felt good warming up, but I wasn’t able to make pitches. I was up in the zone, and that was the game right there.”