The Mets are determined not to make the same mistake twice.

They let Gary Sheffield slip through their fingers last spring and paid a heavy price, falling out of the race in a weak NL East after making it to the World Series the previous season.

They don’t want the same thing to happen next season, especially since the Yankees are expected to steal the off-season thunder by signing free agent Jason Giambi.

Sheffield is at the top of the Mets’ trade wish list, according to industry sources, and it will be up to GM Steve Phillips to pull off a deal with the Dodgers to acquire the slugging outfielder, who has two years and $22 million left on his contract.

The Dodgers need a closer, a center-fielder and a starting pitcher, so this shouldn’t be the most difficult trade in the world to make, unless the Dodgers acquire a closer somewhere else, someone like Troy Percival from Anaheim.

“The Mets definitely have what the Dodgers want,” one NL player personnel director said yesterday. “This deal can get done.”

The Mets are one of the few teams who can satisfy the Dodgers’ needs. Closer Armando Benitez, center-fielder Jay Payton and left-hander Glendon Rusch are all pawns in the Sheffield action.

Sheffield has desperately wanted to come to the Mets for years, but the Mets have been unable to get the deal done. The Mets’ fallback plan includes Milwaukee’s Jeromy Burnitz.

To have a lineup that boasts Mike Piazza and Sheffield will take care of the Mets’ many hitting woes. The National League average for runs scored in a game this past season was 4.70. The Mets averaged 3.96.

Sheffield is a run producer, just like Piazza. Look at these similar numbers. Piazza has hit 314 lifetime home runs, while Sheffield has 315. Sheffield owns 1,016 RBIs to Piazza’s 975. Piazza’s lifetime batting average is higher at .325 to Sheffield’s .295 and Piazza boasts a .579 slugging percentage to Sheffield’s .521.