Yusmeiro Petit is the latest veteran reliever to finalize a deal with the Nationals (AP Photo/Patrick Semansky, File)

The Nationals made their deal with right-handed reliever Yusmeiro Petit official Monday afternoon, a move that filled their 40-man roster and added a fourth new reliever to their rebuilding bullpen. Petit, 31, signed a one-year deal with a club option for the 2017 season, and is guaranteed $3 million in the deal — $2.5 for 2016 and a $500,000 buyout of that option.

Petit joins Oliver Perez and Shawn Kelley as veteran relievers joining the Nationals’ bullpen over the past 10 days, a substantial overhaul of the middle relief corps that required three deals costing $25 million combined over the next three years. Petit is the most versatile of the three veterans, capable of a spot start, late-inning work, and long relief — such as the six innings of shutout work he engineered against the Nationals in Game 2 of the 2014 National League Division Series.

In four seasons with the Giants, Petit made 90 appearances, 57 of which lasted more than an inning. He held right-handed hitters to a .214 average over the past two seasons, and struck out more than a fourth of the righties he has faced in that span. Petit was 3-0 with a 1.42 ERA during the Giants’ 2014 World Series run.

The Nationals’ bullpen — which still includes Drew Storen and Jonathan Papelbon, though President of Baseball Operations Mike Rizzo is open to offers for both — now features four pitchers who have pitched parts of at least seven seasons in the big leagues. Last year’s opening day bullpen had one such pitcher: lefty Matt Thornton.