Nationals trade for A's relievers Sean Doolittle, Ryan Madson

Looking to fortify a bullpen that has blown more than one-third of its save chances, the Washington Nationals acquired relievers Ryan Madson and Sean Doolittle from the Oakland Athletics for right-hander Blake Treinen and a pair of prospects.

The prospects headed to the Athletics are left-hander Jesus Luzardo and third baseman Sheldon Neuse.

Washington has been looking for help at the back end of its bullpen. Treinen, 29, started the season as the closer and is 0-2 with a 5.73 ERA and two saves in 37 innings. He is one of six pitchers with at least two saves for Washington, but nobody has more than Koda Glover's eight, and he is on the disabled list.

The National League East-leading Nationals have a strong rotation led by Max Scherzer (11-5), Stephen Strasburg (9-3) and Gio Gonzalez (8-4) but have converted just 22 of 36 save chances.

Among their starters, the Nationals rank third in the majors in ERA (3.61) and second in opposing batting average (.232), but their bullpen is last in both categories, according to ESPN Stats & Information.

Doolittle, 30, is 1-0 with a 3.38 ERA, three saves and 31 strikeouts in 21 innings. He has held left-handed batters hitless in 23 at-bats this year with 12 strikeouts and zero walks.Doolittle had a career-high 22 saves in 2014.

"I spent 10 years of my life in this organization, so it's weird to be leaving it," Doolittle told reporters Sunday. "I'm super grateful for the opportunity the A's gave me, allowing me to transition to pitching."

Doolittle, who was part of three straight postseason appearances for the A's from 2012 to 2014, called leaving Oakland "really surreal."

A 36-year-old right-hander, Madson has a 2.06 ERA in 39 innings and is seventh among relievers in WHIP at 0.79. He has not allowed any of the seven inherited runners to score in his past 13 appearances and has held opponents to a .188 batting average.Madson had 30 saves for Oakland last season.

Bullpen issues helped lead to the Nationals' elimination in the NL Division Series in 2012, 2014 and 2016. The franchise has never reached the World Series.

Glover converted eight of 10 save chances but has not pitched since June 10 because of severe inflammation of the rotator cuff.

Washington assumes the rest of Madson's $7.5 million salary this season and his $7.5 million salary for 2018. The Nationals also will take over the remainder of Doolittle's $2.6 million salary this year and his $4.35 million pay in 2018. Washington acquires options for Doolittle at $6 million for 2019 and $6.5 million in 2020, with a $500,000 buyout if either is declined.

In addition, the Nationals must pay $250,000 assignment bonuses to both pitchers.

Luzardo, 19, is a 2016 third-round draft pick who underwent Tommy John surgery in March 2016. He has made three starts in rookie ball this season, going 1-0 with a 1.32 ERA.

Neuse, 22, was a second-round draft pick in 2016 and was ranked as the Nationals' No. 7 prospect before the season. He is hitting .291 with nine homers and 51 RBIs for Class A Hagerstown.

Nationals right-hander Joe Ross, who is to have Tommy John surgery Wednesday, was transferred to the 60-day disabled list. The Athletics selected the contract of right-hander Simon Castro from Triple-A Nashville.

The Associated Press contributed to this report.