The Mariners Sunday acquired 1B Yonder Alonso from the Oakland Athletics in exchange for minor league OF Boog Powell. Alonso, 30, is batting .266 with 22 home runs and 49 RBIs. The 2017 All-Star already set career highs in home runs, on-base percentage, slugging and OPS. Among AL first basemen, his .527 slugging mark ranks second, while his 22 homers and .369 on-base mark rank third.
Alonso will platoon at first base, hitting against right-handed pitchers while Danny Valencia will play against lefties. Entering Sunday’s doubleheader in Kansas City, Valencia had an .689 OPS versus righthanders and .873 against lefties.
Alonso will meet the team in Oakland, where the Mariners travel for two games following a day off Monday.
Alonso is on the final year of his contract, meaning he is likely a two-month rental before entering free agency in the off-season.
In a separate deal, the Mariners acquired RHP Ryan Garton and C Mike Marjama from Tampa Bay in exchange for AA LHP Anthony Misiewicz, low-A INF Luis Rengifo and a player to be named later. To make room on the 40-man roster, Seattle designated C Tuffy Gosewisch for assignment.
Against right-handed pitching this season, Alonso is hitting .286 with 18 home runs and 40 RBIs.
In parts of eight MLB seasons with Cincinnati (2010-11), San Diego (2012-15) and Oakland (2016-17), Alonso has combined to hit .269 with 61 home runs and 288 RBIs in 762 games. He was selected by Cincinnati in the first round of the 2008 draft out of the University of Miami (FL).
Powell, 24, hit .194 with two RBIs and in 23 games over three stints with Seattle this season. Powell has spent the majority of the season with AAA Tacoma, batting .340 with six home runs and 33 RBIs in 58 games.
Powell was acquired by the Mariners along with RHP Nathan Karns and LHP C.J. Riefenhauser from Tampa Bay for RHP Danny Farquhar, INF Brad Miller and INF Logan Morrison Nov. 5, 2015.
Garton, 27, made his MLB debut in 2016 and has appeared in 44 games, all in relief. He had three short stints with the Rays this year and has also thrown for AAA Durham where he went 2-0, 1.64.
Marjama, 28, has also spent the season with AAA Durham where he’s hitting .274. Marjama has caught 48 games this season.
Misiewicz, 20, went 8-5 with a 4.75 ERA in 23 starts combined between High-A Modesto and AA Arkansas. Misiewicz was selected by the Mariners in the 18th round in 2015. Rengifo, 20, hit .250 with A Clinton this season. Gosewisch, 33, has spent the majority of the season in Tacoma, but also appeared in 11 games with the Mariners, who claimed him off waivers from Atlanta Jan. 26.
Also Sunday, former Mariners first-round draft choice D.J. Peterson was claimed off waivers by the Chicago White Sox. Peterson, 25, was taken 12th in the 2013 draft but never made the majors, hitting .264 this season for Tacoma before being designated for assignment.