Karstens allowed only four hits to the Astros, who at no point in the game had more than one runner on base. In fact, Houston had just three runners reach second base all evening.
"It was working pretty well. We were able to throw strikes when we had to, bounce the ball when we had to," Karstens said. "We were able to do some good things. Fortunately for me, they were able to go after some of those pitches I was throwing."
For the second start in a row, Karstens held the opposition scoreless in the first inning. In his other four starts this season, Karstens has surrendered one, three, two and four runs in the first frames.
The outing marked just the second time this year that Karstens has pitched at PNC Park, with the other one coming on the second day of the season. Karstens missed about two months with shoulder and hip flexor issues.
"He was like a machine out there, getting strike one right away," right fielder Garrett Jones said. "Nobody was really squaring the ball up. He pitched a heck of a game."
On Thursday, Karstens' counterpart, Astros pitcher Bud Norris, allowed two runs in seven innings. Norris gave up just five hits, while striking out six and walking three.
"I think they had five hits, four of them for extra bases, and we had the four singles," Astros manager Brad Mills said. "He battled through it with runners in scoring position and that was sure nice to see."
The Pirates didn't wait very long to jump on top. Leading off the second inning, Jones pulled a ball that slammed into the right-field wall for a double. He scored when the next batter, Casey McGehee, followed up with another double, this one a bloop shot that landed near the right-field foul line.
The home team scored in the third inning, too, and again Jones was a part of it. With one out and the bases loaded, he stepped in and sent one deep to left-center, trying the opposite field after losing a homer to the tall wall in right. The ball died in the glove of J.D. Martinez before it could land in the seats, but it did go far enough to score Karstens, who had reached third after singling to lead off the inning.
"I had no idea where the ball went," Karstens said about his offensive contribution. "I just kind of hit it, and the fans started cheering, so I figured I'd better run. It's been a long time since I've gotten a hit, and I didn't even use my own bat. I used one of [Jose] Tabata's bats."
The Pirates outscored Houston 27-13 in the four-game set, and Jones had a hit in each one. The right fielder batted .563 (9-for-16) for the series, scoring eight runs and driving in seven more. He also hit two home runs and three doubles.
"I've been feeling a lot more comfortable at the plate," Jones said. "I was getting some balls to hit and just wasn't missing them, and getting the good part of the bat on them."
Joel Hanrahan closed out the game for his second save in as many days. But for the third straight day, the reliever gave the PNC Park cause for concern. Two walks and a wild pitch in a two-run game will do that.
"You never want to put the leadoff guy on base," said Hanrahan, who benefited from a 4-6-3 double play. "I messed that one up, and was all over the zone, a little amped up, I guess."
Before dismantling the Astros, the Pirates' most recent four-game sweep came in 2006 against Milwaukee at PNC Park. In seven games against Houston this season, the Bucs are 6-1.