Diamond had a 2.60 ERA in 34 2/3 innings in Triple-A before posting a 3.54 ERA in 168 innings with the Twins to give him 202 2/3 innings on the season entering Wednesday's start.
But Diamond wanted to make his final start of the year, as the Guelph, Ontario, native has never pitched in Toronto as a big leaguer.
"We've talked about how this might be enough, but he really wants to pitch," Twins manager Ron Gardenhire said. "It's a big start for him. I think, mentally, he really wants this desperately. He thinks it's really important to make this start in Canada, where he's from."
Diamond said he expects to have plenty of family members to watch his start, and didn't want to skip it, despite his jump in innings pitched, as the lefty threw 162 innings last year.
"It's going to be pretty exciting," Diamond said. "I've never been able to pitch there. I'm definitely going to have some friends and family there, so it's going to be kind of a homecoming. I'm pretty excited about it."