The move was made mostly because Dickey has already faced the Orioles three times this season and the Blue Jays would like to avoid increasing that total prior to the All-Star break.
"We looked at it, this would be like the fourth time Dickey has faced Baltimore in the first half and Buehrle hasn't," manager John Gibbons said. "So we just switched that around."
Dickey hasn't enjoyed a lot of success against the Orioles this season. He has allowed 16 earned runs in 18 2/3 innings of work while taking a pair of losses and one no-decision.
The 38-year-old Dickey said part of the decision also had to do with keeping the 2012 National League Cy Young Award winner on normal rest. The Blue Jays had an off-day on Monday and now that Dickey is feeling better on the mound after previously suffering through an upper-back and neck injury, he wanted to settle into a normal routine.
As a result, Buehrle will be making his start in Baltimore on six days' rest. He is 5-5 with a 4.50 ERA in 18 starts.
Gregor Chisholm is a reporter for MLB.com. Read his blog, North of the Border, and follow him on Twitter @gregorMLB. This story was not subject to the approval of Major League Baseball or its clubs.