Jason Grilli (forearm) will begin a minor league rehab assignment Saturday with Double-A Altoona. Grilli will pitch one inning in Double-A on Saturday and Monday before making another one-inning appearance on Wednesday with Triple-A Indianapolis. Barring any setbacks, he could be ready to join the Pirates' bullpen after that. The 36-year-old has been sidelined since late July with a strained right forearm.