"It looked like [Treinen] lost his focus a little bit. That happens to the young guys sometimes," Nationals catcher Wilson Ramos said. "He is really good. When that guy gets a little more experience, he will be a great pitcher."
If there was any good news about that inning, Treinen battled his way out of it by getting Pedro Alvarez to fly out to center fielder Denard Span.
The Nats would tie the game in the fourth, when Ian Desmond swung at a 2-0 pitch from Volquez and hit a mammoth home run over the right-center field fence for his eighth long ball of the season.
But the Pirates retook the lead in the fifth, when McCutchen singled to center field, scoring Harrison. Treinen would last 5 2/3 innings and allow the two runs on four hits. He threw 102 pitches, which was too many, in his opinion. Treinen also was not pleased that he walked five batters.
"I need to execute pitches a little better next time," Treinen said. "My stuff plays [in the big leagues]. I just have to execute pitches. Next time I'm out, I'll do a better job of it."
The Nationals couldn't do anything more offensively, as they went 0-for-8 with runners in scoring position. But they had their chances.
In the second inning, they had runners on first and second with one out against Volquez and couldn't get a run across. They had similar situation an inning later, but this time with no outs and couldn't score.
Volquez would pitch six innings and allow one run on six innings.
"I thought he pitched a really professional game," Pirates manager Clint Hurdle said. "[He] maintained composure, pitched in traffic a couple innings early, gave up the solo home run and just kept pitching. He used the changeup extremely well earlier, quality secondary pitch, the breaking ball played for him and the fastball command was good. It was just a really good effort."
Washington's biggest chance came with the bases loaded in the eighth inning and two outs against left-hander Tony Watson. Pinch-hitter Scott Hairston came to the plate and popped up to Walker to end the threat.
"It was a high fastball. It comes at a three-quarter angle. The ball tends to rise out of his hands. It kind of hard to get on top when he throwing the high fastball. He had good velocity," Hairston said. "The high pitch looks really good to me. I just want to be in position to drive the ball in that situation. At times, I get on top of that ball. Tonight, I didn't. I just missed it. I saw it good. I thought I put a pretty good swing on it. This is a game of inches. Maybe another quarter-inch, the ball leaves the yard. That's how it goes sometimes."
Pittsburgh would add to the lead off reliever Ross Detwiler in the bottom of the eighth inning when Harrison lined a single to right field, scoring Chris Stewart.
In the ninth against closer Mark Melancon, the Nats put runners on first and second with two outs, but Anthony Rendon lined out to McCutchen, who made a sliding catch to end the game.
"[McCutchen] is the MVP for a lot of reasons," manager Matt Williams said. "He is a good player, a really good player. I don't think he is going to go after that ball if he feels like he didn't have a chance to catch it. It was a good play."