The offense was the first to receive reinforcements.

Now it’s the bullpen that gets a key piece.

The New York Mets acquired closer Tyler Clippard and cash considerations from Oakland for minor league pitcher Casey Meisner, the team announced Monday. This deal comes three days after the team acquired veterans Juan Uribe and Kelly Johnson from the Braves.

The Mets trail Washington by two games in the NL East and were 3.5 behind San Francisco for the second wild card before the Giants faced Milwaukee on Monday, and the front office has been active in attempting to find upgrades to fortify the team.

Adding Clippard bolsters a unit that has overachieved thus far while being forced to rely on inexperienced players until Familia could enter the game.

Clippard, 30, has recorded 17 saves and posted a 2.79 ERA in 37 games this season. He’s in the final year of a deal paying him $8.3 million this season, and has appeared in the playoffs before with the Nationals. He began his career with the Yankees.

The right-hander has been good against lefties this year, holding them to a .100 batting average (7-for-70), and that will be of great help to the Mets since they do not have a lefty specialist while Jerry Blevins (fractured forearm) is sidelined.

One cause for concern, though, is Clippard’s walk rate is up from last season and he’s also striking out batters at his lowest rate since 2008.

Adding Clippard lessens the Mets’ reliance on Jenrry Mejia and Bobby Parnell, who have been pitching in the seventh and eighth innings since their recent returns.

While Mejia, who served as the closer last year, has yet to give up a run in 7.1 innings since he’s returned he’s unable to pitch in the postseason due to the 80-game suspension he received earlier this year for testing positive for a performance-enhancing drug.

Manager Terry Collins previously said he has no aversion to using Mejia in high-leverage spots despite the reliever being banned from the postseason, but it would help to have an alternative to use in order to not have to disrupt things should the Mets make the playoffs.

Parnell, who returned from Tommy John surgery, has a 2.70 ERA in 14 games since his return but he does not have the same upper 90s velocity he once possessed.

While the Mets bullpen has been one of baseball’s best this year with a cumulative ERA of 2.86, the relievers have struggled in the second half. In the last 10 games they have allowed 17 runs (13 earned) in 33.1 innings and have blown three saves.

Clippard’s addition gives the Mets four relievers with closing experience, and the team could still be in the market to add another bat to galvanize the lineup.