On the field with a group of reporters at Fenway Park in Boston, Kluber shared the latest as he works his way back from a subscapularis muscle strain.
"The way I felt throwing, the way I bounced back, the calendar, things like that," Kluber said. "I think that's the way I look at it, while not really trying to think I'm up against a timeline."
Kluber last threw off a mound May 25, when the issue surfaced.
"Kluber threw a bullpen today -- 25 pitches," Boone said. "I didn't see it, but I just spoke with him. And my question was, 'Did it go how you would've hoped?' And he said, 'Yes.' So good step for Corey."
On the 60-day injured list since June 5, Kluber is 4-3 with a 3.04 ERA in 10 games over 53 1/3 innings pitched, scattering 21 runs (18 earned) on 41 hits while striking out 55 and walking 23.