In his rehab outing with Double-A Akron on Friday, Kluber threw 47 pitches in five scoreless innings, only allowing one hit and retiring the final 14 batters he faced. In six starts before his stint on the DL, Kluber went 3-2 with a 5.06 ERA.
Armstrong's demotion to the Minors enables struggling starter Danny Salazar to fill the open spot in the Tribe's eight-man bullpen, and it allows the team to maintain right-hander Mike Clevinger -- who was recalled from Triple-A Columbus to start to take the place of the injured Kluber -- in the starting rotation.
In nine relief appearances this season, Armstrong has gone 1-0 with a 6.00 ERA in 12 innings. He has allowed eight runs on 11 hits and six walks with 13 strikeouts.
Indians manager Terry Francona said on Thursday that Lonnie Chisenhall will go through a full-team workout for the second day in a row. While the team will travel to Kansas City on Thursday night for its weekend series against the Royals, Chisenhall will remain in Cleveland on Friday to be re-evaluated by a doctor.
"He's going to go through a full-team workout, which is what he did yesterday, and he actually tolerated it really well," Francona said. "Now, today with a quick turnaround, we're not doing much on the field, but he'll go do everything. He'll run, throw and then he'll be evaluated again tomorrow by the doctor, but he's doing well. He's tolerating everything right now"
The outfielder was placed on the 7-day concussion DL on May 25.
William Kosileski is a reporter for MLB.com based in Cleveland. This story was not subject to the approval of Major League Baseball or its clubs.