Pitch no.73 ended up soaring over the center field wall, however, as Bucs' right fielder Josh Harrison jumped on the first pitch of the sixth and crushed it for a solo blast.
Ten pitches later, after a single by Neil Walker, groundout by Andrew McCutchen and line drive to left by Ike Davis, Fister was lifted in favor of Craig Stammen, who got two outs with one pitch on a double play grounder to third off Pirates' left fielder Starling Marte's bat.
"We've got [Stammen] hot and ready," Nationals' manager Matt Williams explained after the Nats' 5-2 win over the Pirates. "The ball just started to get up a little bit, so, could [Fister] have gone longer? Yeah. But we decided to get him out of there and Stammen came in and made a really nice pitch."
When Fister was done for the day after 5 1/3 IP, the 30-year-old right-hander had lowered his ERA by half a run from 3.93 to 3.42 on the year. After four starts and 23 2/3 IP for the Nationals, he's walked just one batter.
It was Fister's third strong start in a row after a rough outing the first time out against the Oakland A's.
"More of the same," Williams said.
"He worked fast. Changed speeds. Threw strikes. Had some quick innings. The last inning he started to get the ball up a little bit so we decided to go with [Stammen]. But, he came in and did the job and one pitch got us out of the inning. Good job."
Williams explained that it wasn't necessarily the matchup vs Marte, but the idea of giving the Pirates' outfielder a different look that led him to make the change. With two on and one out, he was also looking for a double play.
"Just a sinker baller," the Nats' skipper said. "Just the ability to get a double play. And the fact that Marte had seen Doug a couple times. So give him a little bit different look with a ball boring down in the zone. So it worked good."
With a 2-0 lead early in the fourth game of four with the Pirates and a series sweep a possibility if they lost, Fister, acquired this winter to add a veteran arm to the rotation, provided a calming presence in the finale.
"It's calming with Jordan [Zimmermann] and Stephen [Strasburg] and those guys too," Williams said, "but we needed this one today."
Stammen threw two innings in PNC Park, but when he got in trouble in the eighth, Aaron Barrett took over, allowing one of the runners he inherited to score before shutting the late rally down. Rafael Soriano worked the ninth, retiring the Pirates in order to earn his 11th save and lock down the 5-2 win which left the Nationals 25-25 on the year.