Keller (oblique) threw 43 pitches over three innings during a live batting practice session Wednesday, Alex Stumpf of DKPittsburghSports.com reports.
Keller didn't face any setbacks after throwing 35 pitches Friday, and his return could be coming soon if he doesn't experience any issues following Wednesday's session. The right-hander has been sidelined for over a month with a left oblique strain, but he could get some work in over the final few weeks of the regular season.