Winn will make his first major-league start for the Giants on Thursday in Toronto, Evan Webeck of The San Jose Mercury News reports.
Winn's first three appearances in the big leagues have been in relief, although they've all lasted at least three innings. Nine of the 25-year-old's 12 outings at Triple-A Sacramento this season have come as a starter. That said, while this isn't an opener situation, Winn does figure to have a fairly limited workload Thursday consdering he threw just 44 pitches in his last appearance over the weekend.