Aaron Altherr rounded first base Sunday afternoon, lost his batting helmet and ducked his head for protection. The Phillies stormed out of the dugout almost as soon as Altherr made contact with a walk-off single to clinch a 3-2 win and a four-game sweep of the Pirates. His teammates mobbed him in the outfield grass just past first base, pulling Altherr's jersey and hammering him with fists.

The first four weeks of the season have been a struggle for Altherr. He entered Sunday batting just .104. Even Altherr, one of the most positive presences in the clubhouse, began to wonder whether his luck would change. It finally did Sunday — Altherr came off the bench to go 3 for 3 — and he felt the pain that comes with success. So he lowered his head and absorbed it.

"It felt great," Altherr said. "Just being able to help the team win, first and foremost. But being able to knock in the game-winning RBI is big. The first game-winning one in the big leagues, too. Anything to help the team win. I just want to help the team find a way to win any way that I can."

The Phillies enter Monday's off day just a half game behind the first-place Mets. Their 9-1 start at home is their best mark since 1964 at Connie Mack Stadium. They have won 13 of their last 16 games. And they're doing it with a lineup that has yet to reach its potential.

The Phillies are batting just .230 as a team and five hitters — Altherr, Jorge Alfaro, J.P. Crawford, Pedro Florimon, and Carlos Santana —  are batting worse than .200. Manager Gabe Kapler credited bad luck. His hitters, Kapler said, are hitting balls hard "over and over and not having anything to show for it." Andrew Knapp, who scored Sunday's winning run, pointed to the lineup's ability to work deep counts as the Phillies remain the league leaders for pitches per plate appearance.

Altherr's luck finally changed Sunday. His batting averaged rose by nearly 51 percent. Perhaps good fortune is coming for others, too.

"Once we really start to get going, it's going to be really fun, because we're in these games even when we're not feeling the best at the plate," Knapp said. "That was huge for Altherr [today] to come in and do that off the bench, that just shows that we're still in it, even if the numbers don't say that we're having good at-bats."

Altherr's game-winning single was made possible by Nick Pivetta, who reached the seventh inning, and a bullpen that pieced together 14 outs. Pivetta allowed two runs and struck out seven in 6 1/3 innings.  Tommy Hunter, in his first appearance since being activated from the disabled list, needed just eight pitches to retire the three batters he faced in the eighth. He flashed the cutter that swayed the Phillies to sign the reliever this winter to a $18 million contract.

Pivetta gave up a two-run homer in the fifth but was quick to recover the damage. He drove in Knapp with a double in the bottom of the inning and then, after getting to third on a wild pitch, scored on a shallow fly ball to left. Dusty Wathan, the team's third-base coach, gambled and told the pitcher to tag up. It paid off as Pivetta slid past the tag. Kapler said Wathan had "big stones" on Thursday when he sent J.P. Crawford home from first base on a single. This decision required boulders.

"Openly, I was watching that play, I'm like, 'Oh, my God, I don't even know what Dusty's going to do here.' He did a great job," Kapler said. "He's been incredible. Just a rock on our coaching staff thus far."

Wathan pondered another gamble in the 11th when Knapp skied a fly ball to right that hit the metal fence above the padded wall. It took a bounce and headed back toward the infield. Knapp kept running and may have had a shot to score but Wathan held him up at third. Knapp and Kapler agreed that it was the right call.

"After catching 11 innings, my legs probably weren't in the best spot," Knapp said. "I might have run out of steam."

And then Altherr came to the plate. The Pirates infielders crowded the grass and Altherr roped a single through the left side. Knapp, with time to rest his legs, scored with ease. He threw his helmet in the air and ran toward first base, joining the mob that was mugging Altherr. It was the team's second sweep in a week. Altherr's luck had finally changed. And the punches were welcomed.

"We're having a lot of fun," Kapler said. "I think having fun in baseball is really important. It's a long season. We take it seriously and we prepare like animals, but we also enjoy each other's company, and we're laughing a lot and having a lot of fun, and that leads to confidence."