Richmond's return and Hayhurst's departure mean left-hander Brian Tallet, who has made 18 starts for the Jays this season, will shift back to the bullpen. Tallet moved to the rotation in April due to a wave of injuries facing the staff.
The 31-year-old Tallet, who has gone 5-6 with a 5.09 ERA in 22 appearances for the Blue Jays, already has established a career high with 109 2/3 innings. The lefty's previous career mark was 62 1/3 innings as a reliever for Toronto in 2007.
Richmond, a 29-year-old rookie and one of six first-year starters to pitch for the Jays this season, has gone 6-5 with a 3.69 ERA in 16 games for Toronto this year. Richmond, who was shelved with soreness in his right arm on July 1, will open the upcoming weekend series with the A's. Rookies Brett Cecil and Ricky Romero will have their starts pushed back to Saturday and Sunday, respectively.
Hayhurst posted a 1.72 ERA in 12 appearances for the Blue Jays, during which he struck out nine and walked eight over 15 2/3 innings.
Jordan Bastian is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.