Sellers, 28, played in the majors for parts of four seasons with the Indians and Los Angeles Dodgers. Cleveland acquired him in March, but he made only 21 plate appearances with the team. In 395 plate appearances for the Clippers, he hit .254 with a .307 on-base percentage and a .335 slugging percentage.
The Pirates also activated Charlie Morton from the 60-day disabled list. To make room for Sellers and Morton on the 40-man roster, Pittsburgh designated right-handers Jeanmar Gomez and John Axford for assignment. Both are former Indians.