MIAMI — Johan Santana and one big inning were all the Mets needed.

Santana struck out eight in seven dominant innings, David Wright hit a three-run double and New York opened its season with a 7–2 win yesterday over the Florida Marlins.

If only the Mets had Santana last September, when they blew a seven-game lead in the NL East with 17 games left. The collapse became complete when the Marlins scored seven times off Tom Glavine in the first inning on the season’s final day.

Santana — who was traded to the Mets from Minnesota this winter and wound up signing a $137.5 million, six-year contract with New York — didn’t need much help in his anticipated debut.

The two-time Cy Young winner struck out Hanley Ramirez to begin the game and Matt Treanor to end his outing. Santana (1–0) allowed three hits.

Wright and Carlos Beltran each doubled twice for the Mets. Jose Reyes added two hits for New York, which has now won 30 of its last 39 openers.

The Mets took command with their biggest inning on an opening day, scoring six runs in the fourth against Mark Hendrickson (0–1). Beltran led off the inning with a double and Angel Pagan, Mets newcomer Ryan Church and Reyes hit RBI singles. A walk to Luis Castillo loaded the bases for Wright, who began the game with a career .462 average in that situation.

No surprise, then, that his liner rolled all the way to the left-center field wall, giving the Mets a 6-0 lead. The Mets’ previous biggest burst in an opener was five runs in the seventh inning in a win over the Chicago Cubs at Wrigley Field on April 5, 1979.

The Mets batted around for so long, they might’ve thrown Santana off his rhythm.

Santana retired the first nine Marlins he faced, then went 28 minutes without throwing a pitch while his teammates kept piling up runs.

Ramirez drew a leadoff walk and, two outs later, Josh Willingham homered to left field.

Santana set down seven of the next nine batters, striking out five. When he walked off the field after the seventh, the decidedly pro-Mets crowd of 38,308 at Dolphin Stadium gave him a long cheer.

With Santana out of the game, Florida tried to rally in the eighth, putting runners on second and third with two outs. Jorge Sosa, the third Mets pitcher of the inning, came on and struck out Willingham.

Marlon Anderson singled and eventually scored from second after Matt Lindstrom’s wild pitch in the ninth to give the Mets a 7–2 lead.

Notes: Florida has lost 11 of 12 at home against the Mets since September 11, 2006. … Treanor, making his first opening day start, threw out Reyes — who stole 78 bases last year — at second to end the sixth. Treanor easily caught Wright trying to steal third in the seventh.