La Stella has a $3.25 million, one-year contract that pays $1,203,704 prorated with the Angels, who acquired him from the Chicago Cubs in November 2018. He is batting .273 with four homers and 14 RBIs this season while playing second base and first base for struggling Los Angeles, which began Friday in last place in the American League.
The trade adds another potent veteran bat to the AL West-leading A's, along with depth and versatility at key infield positions. La Stella also was an exceptional pinch-hitter for the Chicago Cubs before emerging as an everyday player with Los Angeles, and that skill could be valuable once again in a postseason run.
''Oakland is getting themselves a championship-caliber player and one that's going to be able to help them as they make their push,'' Angels general manager Billy Eppler said. ''Tommy was a well-thought-of teammate, somebody that cared and somebody that was consistent, showing up with the same demeanor in good times or not. We'll miss him for that.''
La Stella became a first-time All-Star at 30 last season with the Angels after a career spent mostly as a pinch-hitting specialist with the Cubs. He didn't get to play in the All-Star Game because he broke his leg on a foul ball shortly after being selected, but he fought to return to the Angels' lineup late in the season.
La Stella batted .295 with 16 homers and 44 RBIs in just 80 games last season for the Halos.
Joe Maddon, his manager with the Cubs and the Angels, nicknamed La Stella ''3 a.m.'' because of his belief that La Stella could be awakened from bed in the middle of the night and immediately begin hitting line drives.
Barreto has barely played recently for the A's, with the former elite prospect struggling to be consistent in the majors. He is only 0 for 10 at the plate this season with Tony Kemp playing almost every day at second base, although Barreto remains a solid defensive player.
''He's a young kid that has a lot of good years ahead of him and hopefully can bridge that gap between potential and production in the major leagues,'' Eppler said.
Barreto has a $568,500, one-year contract that pays $210,556 prorated. He could be eligible for arbitration for the first time after the 2021 season.
Barreto doesn't have a clear role this season with the Angels, who already have budding star David Fletcher playing every day at second base after shortstop Andrelton Simmons' return from a sprained ankle. Luis Rengifo backs up at both spots, although he was optioned to the Angels' alternate training site in Long Beach earlier Friday.
But Eppler was thinking to next year with the deal. Simmons also will be a free agent this winter, and the four-time Gold Glove winner is another obvious trade candidate in the Angels' disappointing season.
''I like the fact that (Barreto) can play a lot of different positions -- second, third short ,even the outfield,'' Eppler said. ''That's an advantage for our roster, not only now but moving forward as we look to 2021.''
AP Baseball Writers Janie McCauley and Ronald Blum contributed to this report.
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