According to Susan Slusser of the San Francisco Chronicle, the Athletics have placed pitching prospect Michael Ynoa on their 40-man roster.

Leon, Green, Peterson, Ynoa all added to 40-man roster, won't be available in Rule 5 draft. #Athletics

— Susan Slusser (@susanslusser) November 20, 2012

This move is a bit of a surprise, as the right-handed pitcher has never pitched in a full season league.

The Athletics signed Ynoa to a 4.25 million dollar signing bonus in 2008, which is the largest bonus the club has ever given out. Ynoa struggled with injuries and was able to get back on the mound this year, pitching for the Short Season-A level Vermont Lake Monsters.

In 20.2 innings in the NY-Penn League this year, the 21 year-old Ynoa pitched to an ERA of 6.97 and posted a strikeout to walk ratio of 1.19. Reports this summer were that his fastball was topping out at 93 mph.