The Diamondbacks optioned Walston to Triple-A Reno on Thursday.

The Diamondbacks recalled Walston from Triple-A Reno on Sunday.

The Diamondbacks reinstated Walston (elbow) from the 15-day injured list and optioned him to Triple-A Reno on Monday.

Walston (elbow) struck out five and allowed two hits and no walks over 3.2 innings in a rehab start for Triple-A Reno on Sunday.

Walston (elbow) threw live batting practice Friday, Jesse Friedman of GoPHNX.com reports.

Walston (elbow) isn't expected to return from the 15-day injured list until sometime in August, Theo Mackie of The Arizona Republic reports.

Alex Weiner of ArizonaSports.comWalston was placed on the 15-day injured list due to left elbow inflammation, Weiner reports.

Walston did not factor into the decision in Tuesday's win over the Giants, allowing two runs on two hits and four walks while striking out two over 4.1 innings.

Walston is scheduled to start Tuesday's game against the Giants at Chase Field.

Walston is slated to start Saturday's game against the Mets at Citi Field.