Saunders has played 10 games with Tacoma as he works back from a strained right oblique that landed him on the disabled list on July 11, but that return already was interrupted once by paternity leave when he flew home to be with his wife for the birth of their second child.
Saunders has hit .257 with 14 walks in his 10 games so far and even before he got sick, McClendon said the six-year veteran needed to get sharper at the plate before he'd be recalled. Now he'll likely need even more time, with his 20-day stint due to run out on Aug. 26.
The Rainiers season runs through Sept. 1, and it's possible the Mariners could recall Saunders at the end of his 20 days and then ask for an extension that would allow him to continue the Minor League rehab until he's ready.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.