Keller's contract was selected from Triple-A Indianapolis on Tuesday, Rob Biertempfel of The Athletic reports.
Keller was added to the 40-man roster for Rule 5 protection. He appears to be closing in on a promotion to the big leagues, especially after getting called up to Triple-A at the end of June last year. Keller posted a 4.82 ERA with 57 punchouts over 52.1 frames (10 starts) with Indy and could make his major-league debut in 2019.