Chicago Cubs' Dansby Swanson runs to first base for a two-run single during the ninth inning in the second game of a doubleheader against the New York Mets on Wednesday in New York. (AP Photo/Frank Franklin II)

NEW YORK (AP) — Thanks to a historic doubleheader performance Wednesday, Dansby Swanson posted the best four-game series in Chicago Cubs history — with a game to spare.

Swanson had a go-ahead RBI triple and four RBIs to cap the monster doubleheader and lead the Cubs to a sweep of the reeling New York Mets with a 10-5 win.

Swanson hit a three-run homer and a grand slam in the Cubs’ 10-3 victory in the opener. The 11 RBIs in a doubleheader are a franchise record, breaking the mark of 10 set by Hall of Famer Ron Santo on July 6, 1970.

The only other player in team history with a nine-RBI doubleheader is also a Hall of Famer — Billy Williams, who did it on Aug. 21, 1968.

“A dream come true, just being able to have your name next to those guys,” Swanson said. “It’s amazing and special.”

The 11 RBIs are tied for the third-most in a doubleheader. Nate Colbert had 13 RBIs for the San Diego Padres on Aug. 1, 1972, a mark equaled by the St. Louis Cardinals’ Mark Whiten on Sept. 7, 1993.

“Dansby had an incredible day of baseball offensively, for sure,” Cubs manager Craig Counsell said. “It’s fun to see.”

Swanson also homered Tuesday night and logged three homers and 15 RBIs in the first three games of the series, which was slated to conclude Thursday night.

The 15 RBIs are the most ever by a Cubs player in a series of four or fewer games since 1920, when the RBI became an official statistic, and are the most by a Chicago player in a series of any length since Kiki Cuyler, another Hall of Famer, had 15 RBIs in a five-game set in 1932.

The 15 RBIs over the last three games are also the most ever by a shortstop, breaking the mark of 14 RBIs set by Nomar Garciaparra with the Boston Red Sox from May 10-12, 1999. The only other Cubs player with at least 15 RBIs in a three-game span is Sammy Sosa, who had 16 RBIs from Aug. 10-12, 2002.

“I couldn’t tell you a game that I’ve had like this,” Swanson said. “It’s one that you honestly dream about.

“Just very, very grateful.”

The three-game surge snapped a lengthy slump for Swanson, who entered Tuesday hitting .178 with three homers and 14 RBIs in his last 48 games dating back to April 24. Swanson is batting just .202 with a .688 OPS this season — down considerably from his career marks of .251 and .732, respectively, entering 2026.

The Cubs, meanwhile, have patched a hole in their depleted rotation by acquiring struggling left-hander David Peterson in a trade with the Mets.

The Cubs placed Ben Brown and Edward Cabrera on the 15-day injured list on Wednesday, adding to their injury woes in their rotation. Brown has a neck strain, and Cabrera is sidelined with a left hamstring strain.

New York received minor league slugger infielder Cole Mathis in the trade. The 22-year-old Mathis, a second-round pick in the 2024 amateur draft, is batting .272 with 10 homers and 39 RBIs in 39 games over two stops this year.

The 30-year-old Peterson is 3-6 with a 6.09 ERA in eight starts and eight relief appearances this year. He is eligible for free agency after this season.

In a corresponding move, the Cubs designated right-hander Yosver Zulueta for assignment.

Peterson was terrific for much of last year, making the NL All-Star team and throwing his first career shutout while going 8-5 with a 3.18 ERA in his first 24 starts. But he had a 10.36 ERA over his last six starts, and the rough finish carried over into this year.