In a classic swap of players coming off disappointing seasons, the Giants acquired outfielder and leadoff man Angel Pagan from the New York Mets in exchange for center fielder Andres Torres and right-hander Ramon Ramirez Tuesday night.

All three players were eligible for arbitration and not certain to be tendered contracts by Monday’s deadline. The deal, the structure of which was first reported by Bay Area News Group, is pending a physical and might not become official until later this week.

Torres and Ramirez were hugely productive in 2010 while helping the Giants to the NL West title on their way to the World Series. Torres, in particular, emerged as a fan favorite because of his energy and gallantry, along with his gliding defense in center field. But he struggled mightily with physical and mental issues in 2011 and was no longer seen as an everyday solution.

Pagan also had a come-down from a big 2010 season but is seen as a more bankable producer in the leadoff spot. The 30-year-old is also two years younger than Torres. He hit .262 with a .322 on-base percentage and 32 steals; he had 24 doubles, four triples and seven home runs among his 127 hits.

The Mets are said to value defense in center field and they consider Torres a clear upgrade over Pagan in that regard. Anyone who watched Torres play in the pastures of the NL West the last two years would agree; he probably deserved a Gold Glove in 2010.

Pagan played all of his defensive innings in center field, and committed a whopping 10 errors. (Arizona’s Justin Upton (13) was the only NL outfielder to commit more.) While it’s easy to assume the Pagan acquisition will bump Melky Cabrera to left field, the Giants wanted to give Nate Schierholtz more competition for the everyday right field job, too.

Ramirez was sensational after being acquired at the 2010 trade deadline and he was almost as good last season, posting a 2.62 ERA while tossing 68.2 innings in 66 appearances. But the Giants have a lot of right-handed relievers in their system — prospect Heath Hembree is coming quick — and considered Ramirez more expandable.

The Giants likely saved at least $2-3 million in the trade and they could use that flexibility any minute now. Sources said the Giants are far down the road on a second trade proposal with an American League club, possibly involving infielder Jeff Keppinger.

Sources said the Giants aren’t in on talks on White Sox’s Carlos Quentin or the Red Sox’s Jed Lowrie — two Stanford alumni whose names have been buzzing around the lobby. Atlanta’s Martin Prado is a versatile infielder who could play at four spots, but the Giants haven’t pursued him, either.

More as it happens…