Blue Jays manager John Gibbons announced Thursday that left-hander J.A. Happ will start against the Phillies on Monday as the beleaguered club switches to a six-man rotation, reports Brendan Kennedy of the Toronto Star.

"We'll see where that takes us," said Gibbons, whose starters combined to throw 147 innings in April, the fifth-fewest in the major leagues.

Happ was expected to land a spot in Toronto's rotation out of Spring Training, but an untimely back injury - and four atrocious Grapefruit League outings - forced him to open the season on the disabled list. The 31-year-old was activated April 15, and has crafted a 4.15 ERA over three relief appearances thus far, issuing five walks in 4 1/3 innings.