Keller isn't an immediate candidate for recall as the organization would like him to focus on adding a new pitch (a slider/cutter) to his repertoire at the Triple-A level, the Pittsburgh Tribune-Review reports.
"He's gaining some confidence in it (the slider/cutter) and some willingness to use it in key situations," general manager Neal Huntington said. Pittsburgh will start Steven Brault and Nick Kingham on Tuesday and Wednesday, and hope to have Chris Archer back in a week. Keller, who's totaled 16 starts at the Triple-A level, has struggled with his control (14 walks in 31 innings) but posted a 16:2 K:BB in his last two games. "Keller is making great strides," Huntington said. "His last two starts are really reasons for us to continue to be optimistic about Mitch." For the season, the 23-year-old has registered a 3.48 ERA and 1.55 WHIP. More than ever, it seems likely he'll be up before September -- provided he continues to show improved control and command.