The move creates more roster flexibility for the Rays. Assuming the club reaches the postseason, it can use Riggans' roster spot to add someone who wasn't in the Majors as of Aug. 31.
Realistically, one of the backup options -- John Jaso or Michel Hernandez -- would have to be added because both players were called up in September.
Hernandez made his Rays debut in the first game of Saturday's doubleheader at Yankee Stadium and could get a second start during this weekend's four-game set against the Twins. Rays manager Joe Maddon said on Thursday that he had hoped to rest starter Dioner Navarro over the weekend and heading into a tough final week of the regular season, which includes a doubleheader on Tuesday.
Jaso, who began the season in Double-A Montgomery, has yet to start but appeared behind the plate in Monday's loss, recording his first Major League hit.
Although the Rays have relied heavily on Navarro, the bulk of Riggans' playing time likely will go to the more experienced Hernandez, who was selected from Triple-A Durham on Sept. 9.
Hernandez, 30, was acquired from the Pirates for cash considerations on Aug. 31, joining Durham's postseason roster. He hit .266 this year with three home runs and 17 RBIs in 76 games for Triple-A Indianapolis.
Brittany Ghiroli is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.