The first quarter of the season hasn’t played out perfectly for the Giants, but they’ve still managed to defy expectations and retain their surprise hold on first place in the tightly contested National League West.

After enduring back-to-back walk-off losses, the Giants rebounded to defeat the Pirates, 4-1, on Sunday afternoon for a split of the four-game series at PNC Park.

At 24-16, San Francisco owns the best record in the NL and remains ahead of the division-rival Padres and Dodgers through its first 40 games. Even so, the club will head to Cincinnati feeling like it missed an opportunity to create more separation atop the NL West standings, if the bullpen could have locked down the middle games of this series with the Bucs.

“I think we have a better brand of baseball in us than we played in this series,” manager Gabe Kapler said. “I think their club is very well-coached, very well-managed. They’re tough. I think [Pirates manager Derek Shelton] and his staff had their team ready to play in this series, and they scratched and clawed for every base and every pitch. I have a lot of respect for how they played this series.

“I also think we’re better than we showed in this series. We need to bring our 'A' game every time because Major League teams are really good, and if you don’t bring your best baseball, they’re going to beat you.”

Left-hander Alex Wood improved to 5-0 after striking out six over six innings of one-run ball, lowering his ERA to 1.75 on the season. The 30-year-old is the first Giants pitcher since Madison Bumgarner in 2012 to win five of his first six starts, and Wood is the first since Barry Zito in 2010 to go undefeated over that span.

Mike Yastrzemski launched a two-run home run in the top of the ninth for some much needed breathing room, and Buster Posey was 3-for-4 with a walk to boost his batting average to .382, the highest mark in the Majors among hitters with at least 50 at-bats this season.

After blowing late-inning leads on Friday and Saturday, San Francisco’s bullpen bounced back as Caleb Baragar, Matt Wisler and Tyler Rogers combined for three scoreless innings in the finale.

The Giants’ sterling starting rotation, which leads the Majors with a 2.76 ERA, has carried the club thus far, but the bullpen has emerged as the biggest concern after posting a 4.27 ERA with 12 blown saves, tied with the Dodgers for the most in the big leagues.

Rogers (0.79 ERA) has established himself as Kapler’s most trusted reliever, but closer Jake McGee (5.09 ERA), rookie Camilo Doval (8.38 ERA), Wisler (6.75 ERA) and Jarlín García (5.79 ERA) have stumbled early this season. Reyes Moronta (right flexor strain) and José Álvarez (right ankle sprain) are also on the injured list, limiting the club’s back-end options.

Baragar and Wisler could end up being part of the solution. Wisler used 13 sliders to post a 1-2-3 seventh inning, flashing the unique skill set that convinced the Giants to sign the 28-year-old right-hander to a one-year, $1.15 million deal in the offseason.

“Wisler’s inning stood out as really important,” Kapler said. “He’s a guy that we started this season feeling like we were going to lean on in big moments. We wanted to see how he’d handle leverage innings for us. I think he’d tell you that the season didn’t get off to the best start for him, but we never lost confidence in him, and he certainly never lost confidence in himself. We feel good about giving him an opportunity now to try to kind of take down a meaningful role for us in our bullpen, and we believe he can do that.”

The Giants’ offense still isn’t clicking as expected, but the lineup is getting a bit healthier. Yastrzemski, who missed one game with soreness after crashing into the right-field wall on Friday, made his return, along with Alex Dickerson, who was activated from the IL after missing eight games with a right shoulder impingement. Donovan Solano is getting closer after going 3-for-3 in his first rehab game with Triple-A Sacramento on Saturday.

While the bats have struggled to consistently take some pressure off the pitching staff, the defense has emerged as another strength.

Wood limited the damage with the help of second baseman Mauricio Dubón, who made a pair of spectacular plays to defuse a potential Pirates rally in the fifth. After Adam Frazier led off the inning with a single, Dubón ranged far into foul territory to make an impressive snag in front of the protective netting on Kevin Newman's popup.

Bryan Reynolds followed with another hit to put runners on the corners with one out, but the former Giants prospect then found himself caught in a rundown on an attempted steal of second base. Dubón took a throw from Posey and forced Reynolds to retreat to first base before alertly firing to Evan Longoria to nab Frazier at third and preserve a 1-1 tie.

“I just watch the game and trust my instincts,” Dubón said. “That’s all I can do. If I overthrow it or the guy is safe, I get my head chopped off. But it ended up working. I take pride in my instincts.”

Earlier in the series, Dubón flashed his athleticism when he sprinted into center field to make an incredible catch on a blooper off the bat of Gregory Polanco on Saturday. Now that he’s drawing most of his playing time in the infield, Dubón has been using a glove that was given to him as a gift by three-time Gold Glove Award winner Brandon Crawford, who Dubón said he’s been trying to emulate.

“Have you guys seen the movie, ‘Like Mike?’” Dubón asked. “Somebody wears Michael Jordan’s shoes and all of a sudden he’s good at basketball. That’s one to keep. It’s been mine for a while now.”