PHOENIX -- The D-backs may not have an exact timetable just yet, but it seems Shelby Miller is nearing a return.
In his latest rehab start for Class A Advanced Visalia on Saturday, the right-hander tossed 6 2/3 scoreless innings. He struck out 10 and walked none, throwing 81 pitches.
"He's getting close," D-backs manager Torey Lovullo said. "With these outings and the feedback he's giving us, he's telling us that he's getting closer every day."
Lovullo said Miller, who had Tommy John surgery last May, is headed back to Arizona, where the athletic training staff will assess him. They will formulate a plan for his next steps, which Lovullo will know more about Monday when the D-backs are in Anaheim. 
Miller's latest outing was the best since he began his rehab stint. It was encouraging, especially because Miller allowed eight runs over three innings in a June 10 start for Visalia.
"We're not so concerned about the results, but the results matched how he felt, so that's a very good sign," Lovullo said of Miller's most recent start.
The D-backs had to tinker with their rotation to account for injuries early in the season. Everything considered, that situation has turned out well.
Matt Koch has filled in nicely for Taijuan Walker (Tommy John surgery) and Clay Buchholz has pitched well in the spot left by Robbie Ray (oblique) since the D-backs signed him last month. No D-backs starting pitcher has been shaky enough to warrant being replaced.
So, with every spot in the rotation taken, whom will Miller replace? The righty has been a starter his entire career. He was an All-Star for the Braves in 2015 when he posted a 3.02 ERA over 33 starts.
With Arizona in 2016, Miller tallied a 6.15 ERA over 20 starts. He also spent time in the Minors that season.
When asked if the D-backs would use Miller as a starter or in a bullpen role upon his return, Lovullo said that decision is to be determined.
"We're stretching him out like a starter, I think Shelby thinks like a starter," he said. "So I think that's where our thoughts, first and foremost, go to, when we're thinking about Shelby."