The versatile Kemp began last season with Houston, where he played from 2016-2018. On Monday, Astros manager AJ Hinch and general manager Jeff Luhnow were fired after the pair were suspended by Major League Baseball for the team's use of electronics for sign-stealing during Houston's run to the 2017 World Series title and again in the 2018 season.
Kemp batted .212 with eight home runs and 29 RBIs over 110 games between the Astros and Cubs last year. He started 30 games at second base, nine in left field, nine in center field and three in right field.
Rivas batted a combined .292 with nine homers and 60 RBIs over 122 games between Single-A Stockton - 114 games there - and Triple-A Las Vegas.
Oakland's 40-man roster is full.
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