The 24-year-old Petit went 3-10 with an ERA of 5.82 and a 1.52 WHIP in 89.2 innings (23 G/17 GS) last year.
Petit posted a solid K/9 rate of 7.43, but his BB/9 rate sat at 3.41, and he gave up 19 HRs.
Moving to pitcher-friendly Safeco Field and the Mariners' tough defense helps, but he needs to improve his fly ball rate (and home run rate) and walk rate to become a better pitcher.
He's still young, so if he can turn it around with Don Wakamatsu and Rick Adair, he may crack the rotation.
Another low-risk, high-reward move by Jack Zduriencik.