CHICAGO -- There has been many a time in recent years where the Pirates were quiet postgame in Wrigley Field’s visitors’ clubhouse. Not Sunday, though. Nor Thursday or Friday.

In what was their biggest road series so far this season, the Pirates left Chicago with a series win, taking a third contest in the four-game set with a 3-2 win Sunday. A year ago, the Pirates won just three games against the Cubs. They did it in a weekend series this season, and they did it with starting pitching leading the charge.

Mitch Keller was the fourth pitcher to deliver a quality start, allowing two runs on two hits. That followed Bailey Falter going 7 2/3 scoreless innings on Saturday, Paul Skenes twirling six no-hit innings Friday and Jared Jones striking out seven with no walks over six innings of three-run ball.

“Everyone went out,” said Nick Gonzales, who had two hits Sunday, including an RBI single. “Jonesy, Mitch, Bailey, everybody. It was really impressive.”

In total, that’s 25 2/3 innings pitched, five earned runs, 23 strikeouts and six walks. According to the Elias Sports Bureau, this is the first time the Pirates got at least 25 2/3 innings of starting pitching at Wrigley Field in a series since Aug. 2-5, 1993. It wasn’t just quantity. It was quality, too.

Sunday was a far from perfect game by the Pirates. They stranded a dozen men on base. They went 1-for-17 with runners in scoring position. Keller was a bit more wild than usual, walking three and hitting two.

Pittsburgh has played far from perfect ball all year, too. The offense has not consistently produced. The bullpen has not often lived up to lofty expectations -- though Colin Holderman, Aroldis Chapman and David Bednar made quick work of the Cubs on Sunday. The defense has been spotty at times.

Despite that, the Pirates are hanging in there because of their rotation, which ranks second in the National League in innings pitched (271 1/3) and fifth in ERA (3.68).

"Starting pitching is the key,” said manager Derek Shelton. “It's why teams win. It's why teams go deep into the season, because if you have that every night, you're going to give yourself a chance … All you ask your starters is give us a chance to win the game, and our guys have done that."

So what makes this group special? When asked, Keller pointed his head over to the lockers of Jones and Skenes.

"Those two are absolutely electric,” said Keller. “That's a good start.”

It’s hard to find fault with that mindset, or the one that the coaches have been preaching to the pitchers all year.

“It's just the best stuff in the zone,” Keller said. “I think it's a great mentality. We all have nasty stuff, whether it's 100 mph fastballs or 97 mph splitters. Just fill it up, put the pressure on them and let our defense play."

“It’s always friendly competition,” Falter said after his start Saturday. “We like to take subtle jabs at each other every once in a while, but it’s been good. We’ve been rolling pretty well.”

The Pirates knew they had the makings of a potentially strong rotation in the near future, which is part of the reason why they were motivated to extend Keller this winter to be a leader for the group. He showed an example of why they trust him Sunday. After a hit batsman and a Cody Bellinger double to open the sixth, the Cubs were in prime position to tie up a 3-1 game, but Keller escaped with only a sac fly allowed to keep the lead intact.

“I think you see the maturity of Mitch Keller with the fact that that's a really tough situation,” Shelton said. “We give up one run, we don't give up two. We give up two and the game [is] tied, it changes the whole dynamic.”

This weekend was potentially a sign of what was to come with some of the young pitchers the Pirates are building around, but they also came into this year with higher expectations. A series win in Wrigley and a winning record on a road trip against the top two teams in the National League Central is a start.

"What we have is really good,” Keller said about the rotation. “What we have coming is really good, too. It's a long season, so we've just got to keep going.”