Sean Manaea’s three-year, $75 million deal was a significant part of what’s been a busy Mets offseason so far — and he hopes it’s not done.

The left-hander has already been teammates in San Diego with newly signed Met Juan Soto and he’s been working out at a gym in Tampa alongside Pete Alonso, who remains a free agent.

“We’ve done an incredible job this offseason: We got Juan and some other things,’’ Manaea said during a Zoom call Monday. “Hopefully, a couple other things happen.”

Manaea said he “very much” wants Alonso to return to the Mets, but the two sides remain apart in their negotiations.

“I’m always gonna support him and I’d definitely love to have him back on the Mets and be our first baseman,’’ Manaea said. “Hopefully, we can get that done, but whatever happens, I’ll be happy for him.”

The two have spent most days at Diesel Optimization in Tampa, although Manaea said Alonso “shows up earlier than I do.”

While Manaea and the Mets wait on Alonso, they’re looking ahead to 2025, which will feature Soto in the outfield with his mammoth 15-year, $765 million deal.

The two played together in San Diego after Soto’s trade deadline arrival from Washington in 2022.

Manaea called Soto “amazing.”

“When he first came over, you could feel his energy and what he brings to the table,’’ Manaea said. “He carried that through the rest of the season and postseason. We have some history. I’m happy he’s here.”

Manaea had a rough ’22 season in San Diego before he signed as a free agent with the Giants, where he also struggled in 2023.

The Mets are counting on Manaea, who turns 33 next month, performing like he did during his first season in Queens, when he rebounded with arguably the best season of his career.

That was backed in large part to a strong second half, during which Manaea had a 3.09 ERA in his last dozen starts of the regular season and three more in the playoffs before a rough outing in the Mets’ season-ending loss to the Dodgers in Game 6 of the NLCS.

Manaea credited the Mets coaching staff — and pitching coach Jeremy Hefner — with helping him make the proper adjustments, as well as stay healthy.

Manaea called the Mets “a perfect fit” in free agency: “It made sense to come back here.”

He pitched a career-high 181 ²/₃ innings and will be in a rotation that lost Luis Severino in free agency — and figures to lose Jose Quintana — but picked up another former Manaea teammate, Frankie Montas.

“I love him to death,’’ said Manaea, who spoke with Montas before the right-hander signed his two-year, $34 million deal earlier in the offseason. “He’s very passionate about pitching and is competitive.”

They’ll join Kodai Senga, who made just one regular-season start due to injuries and then pitched poorly in three playoff appearances, as well as newcomers Clay Holmes and Griffin Canning, with David Peterson, Paul Blackburn and Tylor Megill also returning.

Heading into the final part of the offseason, Manaea said he’s working on his changeup, which he said has been inconsistent in the past.