After Washington (65-81) won the opener 6-2 and Pittsburgh answered with a 5-1 win, the difference so far in the series came Wednesday when Nationals right-hander Jackson Rutledge got roughed up for seven runs in his major league debut and the Pirates hung on for a 7-6 win.
The finale Thursday is the only game where both teams listed projected starters entering the series.
Washington right-hander Josiah Gray (7-11, 4.13 ERA) is scheduled to start opposite Pittsburgh right-hander Mitch Keller (11-9, 4.23).
Keller, who will be making his 100th big-league appearance, has had an uneven second half for the Pirates (68-78).
He is coming off a loss Friday at Atlanta when he allowed eight runs, tying a season high, along with a career-high 12 hits in five innings. It was one of several rough outings he's endured since making the All-Star Game for the first time.
After posting a 9-4 record with a 3.31 ERA in the first half of the season, Keller is 2-5 with a 6.09 ERA since the break.
Keller has pitched 174 2/3 innings, by far a career high, but that's something he is embracing because he wants to build toward being able to be strong into the postseason, at least someday.
"I'm trying to build off last year's innings," Keller said. "Obviously, we're not at the point where we're trying ... to get to the playoffs, but obviously, the next step of this is trying to find my routine so I can feel good hopefully going into postseason baseball."
In the meantime, his velocity has slipped some even though he said he feels good.
"This is a good learning thing by trying to get over the hump here, look at some mechanical things," he said. "I don't know what it might be, but just try to find something to get the (velocity) back up."
Pittsburgh manager Derek Shelton took some of that pressure off Keller.
"We're in the middle of September, so that's going to be typical, a little bit of a trend down," Shelton said. "I don't think that played into it (against Atlanta). I think they just did a good job putting the ball in play."
Against the Nationals, Keller is 0-1 with a 10.57 ERA in two career starts, both last year.
Gray has not pitched since Sept. 3, when he gave up three runs, four hits and four walks in four innings in a no-decision against the Miami Marlins.
It was his second straight rough outing, but something else also stood out from the game against the Marlins. In the first inning, he gave up a leadoff homer to Luis Arraez. Three batters later, rookie outfielder Jacob Young lost a fly ball in the sun for a double. Gray fumed and, when the inning ended, screamed at Young.
"I think that fly ball just threw me for a whirlwind, and I tried to refocus but obviously didn't take long enough to refocus and regain my composure," Gray said. "Just not in character to show that much frustration out there. I ... apologized to the guys about it. I feel terrible about it. I've just got to learn from it."
Against the Pirates, Gray is 1-0 with a 4.91 ERA in two career starts, the win coming April 30 when he held Pittsburgh to one run and three hits in six innings.
—Field Level Media