The 42-year-old Saito has no record with a 6.14 ERA in 10 games with Arizona. Saito was an All-Star in 2007 during a 39-save season with the Dodgers. He totaled 81 saves in his first three major league seasons and has a 2.27 ERA for his career, but has just three saves the last four seasons.
"He's had a hard time staying healthy all year," manager Kirk Gibson said. "He was really sore the other day when the doctors examined him. We're not going to play short at this point."
Saito began the year on the DL with calf and shoulder injuries, and was activated on July 21. Gibson said Saito was injured in his last appearance on Sunday while allowing two runs on three hits, getting just one out in a 7-4 victory over the Nationals.
The Diamondbacks also purchased the contract of left-hander Mike Zagurski from Triple-A Reno. The 29-year-old Zagurski, who was in uniform for Tuesday night's game at St. Louis, was 0-0 with a 6.18 ERA in 32 games with Arizona before he was designated for assignment on Saturday and outrighted to Reno on Monday.
"He got a little three-day vacation. He needed it, his arm needed it," Gibson joked.
Zagurski was claimed by the Diamondbacks off waivers from the Phillies last Sept. 22. He had allowed seven earned runs in 3 1/3 innings his previous six games.