SEATTLE — AJ Ramos was as surprised as anyone when he heard the Marlins had traded him to the Mets.

“I heard all kinds of [rumors], but I didn’t hear Mets at all,” Ramos said Sunday. “When they told me, I had to ask, ‘Wait, are you sure?’ OK, let’s go.”

In his debut with his new team, Ramos allowed two runs on two hits and a walk in the eighth inning of the Mets’ 9-1 loss to the Mariners.

The 30-year-old Ramos, who is arbitration eligible after the season, gives the Mets another proven back end of the bullpen option heading to 2018. With the Marlins this season, he was 2-4 with a 3.63 ERA and 20 saves.

Ramos will assume the closer’s role following the expected trade of Addison Reed. The Mets also remain confident Jeurys Familia will return in the coming weeks from rehabbing his shoulder, following surgery to remove a blood clot.

“These guys have a lot of players here, some great starting pitching, there’s some good chemistry here,” Ramos said. “There’s a lot of injuries that happened this year. I know that and know we’re not far off from competing in the playoffs.”

Ramos has an elongated middle finger on his right hand that he credits for helping him throw his signature splitter.

“It’s a gift and a curse, my middle finger is almost an inch longer than [the index] finger, so that is why my ball has natural cut to it,” Ramos said. “If I’m not in the right position sometimes it gets away from me. If [reporters] get me mad this finger is really big.”

Jose Reyes departed the game after getting drilled in the left forearm, but X-rays were negative.

“Now it’s good,” Reyes said, adding that he’s unsure if he will play Tuesday against the Rockies. “It’s a good thing we’ve got a day off [Monday].”

Josh Edgin was designated for assignment to create roster space for Ramos. The lefty was 0-1 with a 3.65 ERA in 46 appearances for the Mets.

The Mets did not have an extra-base hit in a game for the seventh time this season. Wilmer Flores (2-for-4) was the only Mets player with multiple hits.