Diekman, 36, went 0-1 with a 7.94 ERA in 13 games with the Chicago White Sox this season before being designated for assignment on May 2 and released four days later.
He has a 25-30 record with 15 saves and a 3.96 ERA in 612 appearances during a 12-year career.
The Rays are Diekman’s eighth big league team. His last two outings with Chicago came on April 27 and 29 against Tampa Bay in which he allowed six runs, two earned, over a combined 1⅔ innings.
Tampa Bay’s bullpen is currently without injured closer Pete Fairbanks (inflammation near right wrist) and lefty Garrett Cleavinger, who has what may been a season-ending right knee sprain that occurred Sunday during a rundown between third base and home involving New York Yankees outfielder Aaron Hicks.
Anderson gave up two hits over five scoreless innings in two games.
The Rays acquired him from the Cincinnati Reds on May 3 in a minor league deal for cash.
Anderson, 35, went three innings that night to get his first major league save in the Rays’ 8-1 win over the Pittsburgh Pirates. He had been scheduled to start a game at Omaha the same day for Triple-A Louisville.
The Rays finish a three-game series Wednesday night at the Baltimore Orioles in a matchup of teams with the best two records in the American League.
Rays sign Jake Diekman, designate Chase Anderson for assignment