TAMPA, Fla. — With the Islanders’ playoff elimination at the hands of the Lightning, a summer of uncertainty now begins for three free-agent forwards — all of them drafted by the club and two of them alternate captains — who may have played their last game for the Isles: Kyle Okposo, Frans Nielsen and Matt Martin.

Okposo, 28 — whose first full season with the team was 2008-09 and, along with Nielsen, has the longest tenure of the trio — stands to cash in the most on a new contract.

“It’s such a down losing the series. It’s all tough to digest right now,” said a somber Okposo, who has 139 goals and 369 points in 529 regular-season games as an Islander, plus seven goals and eight assists in 24 playoff games. He had two goals and six assists in 11 playoff games this spring, but only one goal in the second round.

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“I’ll have to reflect on the year and what’s next a couple days from now,” said Okposo, who was paid $4.5 million this season. “The focus was that you’re part of the hockey team, just trying to win one game and extend the series.”

Coach Jack Capuano lamented that the Islanders simply couldn’t score enough against the Lightning, which had 18 goals. After scoring five goals (one an empty-netter in Game 1), the Islanders scored six in the final four. Okposo and Nielsen had 42 goals between them during the season but only one (by Okposo in the 2-1 overtime loss in Game 4 on Friday night) in the series.

“It’s a business and there’s a lot of change. Guys in this business have to move on, and hopefully they don’t,” Capuano said. “We’ll see how talks go . . . To me, Johnny [Tavares], Franzie and Kyle, the leadership that they provided for us down the stretch when we were scratching to get into the playoffs, with all the injuries, they did a great job . . . I’m really proud of them.”

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Nielsen, a 32-year-old Danish center who was drafted in 2002, was 3-3-6 in 11 games and earned $3 million this season. He had no goals and two assists in the five games against the Lightning.

He said the team has been “taking steps in the right direction. I definitely think this team can do some damage in the future. I’ve been proud representing this organization. We’ll see what happens, but I’ve always been proud to wear this jersey.”

Martin, 27, another Islanders draftee (in 2008), led the NHL with 365 hits as a fixture on the fourth line and was a bargain at $1.1 million.

“This was a lot of fun this year. We wanted to go farther. It stings,” he said. “I don’t know what the future holds. I want to spend some time with the guys . . . It’s been a huge honor to wear this jersey for seven years, whatever it’s been. We’ll see what my agent and Garth [Snow, the Islanders’ general manager] and management figure out. Every year you see free agency, trade, retirement, whatever. I’ve played with these guys a long time, and the uncertainty is hard, but it’s the nature of the business. We’ll see how it plays out.”