Rays manager Joe Maddon said Thursday that Longoria, who has been on the 15-day disabled list with a partially torn left hamstring since May 1, will be the designated hitter for Triple-A Durham on Saturday.
The three-time All-Star was hitting .329 with four homers and 19 RBIs in 23 games before getting hurt. Tampa Bay (35-28) has gone 20-20 without Longoria.
Longoria was injured April 30 while running to second base on an attempted steal.
Also, infielder Jeff Keppinger, out with a broken right big toe, will be Durham's DH on Friday.