Kluber, who will start Thursday afternoon's game against the Oakland Athletics, has been sidelined since exiting a game due to lower back soreness on May 2.
"He's not going to pitch all day. I guarantee you that," manager Terry Francona said of Kluber, the 2014 American League Cy Young Award winner. "The key is to win, but also set him up for the rest of the year. We'll keep an eye on him. We'll probably aggravate him a time or two by asking him how he's doing."
Kluber owns a 3-2 mark with a 5.06 ERA in six starts this season.
The 31-year-old allowed just one hit over five scoreless innings in a rehab start on Friday with Double-A Akron.
Armstrong has toggled between Cleveland and Triple-A Columbus for much of the last two seasons. He has a 6.00 ERA and 13 strikeouts in 12 innings with the Indians this season.