Pittsburgh Pirates' Konnor Griffin began a rehab assignment Tuesday with Double-A Altoona. Associated Press

PITTSBURGH — Pittsburgh Pirates rookie shortstop Konnor Griffin began a rehab assignment Tuesday night with Double-A Altoona, the club said.

Griffin has been sidelined since May 31 with a right forearm strain. He made his major league debut with the Pirates on April 3 and was signed to a nine-year, $140-million contract five days later.

Griffin, 20, is hitting .270 with four home runs, 22 RBIs and 14 stolen bases in 51 games this season. The Pirates do not have a timetable for when Griffin will be activated from the injured list.

“We’re going to take it day by day and just see how he’s responding to everything,” Pirates manager Don Kelly said before Tuesday night’s game against Seattle. “Sounds like yesterday and today went well with the challenging throws on relays and stuff in the hole. Just get him back into game action and see how he’s doing with the arm, rhythm and timing of the at-bats. Look to get him back up here soon, hopefully.”

Further imaging on right-hander Jared Jones’ right elbow revealed no damage. Jones left Sunday's game in the third inning after he was hit on the elbow by a line drive from Colorado’s JT Rumfield.

If Jones gets through a bullpen session without incident Wednesday, he will start against Cincinnati on Saturday, the team said.