The Phillies’ bullpen was one of their biggest weaknesses. Now it’s a strength.

With Jose Alvarado back in the picture, at least for the regular season, and Jhoan Duran taking over as full-time closer, the Phillies have more firepower in their bullpen than they’ve had all season.

That’s turned the bullpen from one of the team’s biggest weaknesses into a strength. The Phillies’ bullpen ERA prior to the trade deadline was 4.48. In August, the Phillies’ bullpen pitched to a 3.23 ERA, the fifth best in MLB over that span.

The new depth in the pen gives Rob Thomson the freedom to be more aggressive with his top relievers. Thomson is open to pitching guys three days in a row or four out of five days in the Phillies’ chase for a top-two spot in the NL and a first-round playoff bye.

“It all depends on workload, how many pitches they throw and how many days off they’ve had before that, but I’m not afraid to do it now,” Thomson said.

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Duran blew his first save as a Phillie in the opener against the Nationals, after successfully closing his first six attempts. He allowed two hits on Saturday against the Nationals in the ninth, but did make the save.

The Phillies have a 15-game stretch with no off days in September, with five of those games coming against the Brewers and Dodgers, two of the other top contenders for the first-round playoff bye. Thomson feels comfortable pushing Duran and his other highest-leverage relievers to pitch on consecutive days for the stretch run.

“He hasn’t done it this year, but he’s gone four of five like three, four times when he was in Minnesota,” Thomson said. “I think it all comes back to how many pitches he’s thrown the first two days.”

David Robertson signed with the Phillies at midseason, making his first appearance in the majors this year on Aug. 11 against the Reds. So far, Robertson has delivered in his spots, allowing just one run, a home run to Eugenio Suárez, in five appearances, and struck out 10 in just 5.2 IP. He’s pitched back-to-back games twice.

In his age-40 season, Robertson came into Philadelphia with a fresh arm, and he and Thomson are hoping the extra rest from joining midseason helps keep it that way.

In 2022, his results dropped off dramatically at the trade deadline. After putting up a 2.05 ERA with a 1.0 WHIP in 40 appearances with the Mets, Robertson put up a 5.06 ERA with a 1.594 WHIP in 22 appearances after being traded to the Marlins. Robertson pitched to a 3.00 ERA in 68 appearances with the Rangers in 2024.

“He’s in great shape, but the wear and tear of the first couple of months might hinder a guy moving down the stretch,” Thomson said. “With a guy his age — I mean, he’s a lot younger than I am, but in baseball terms — his experience could help him.”