From ESPN.com:

Oakland Athletics prospect Grant Desme is retiring from baseball to enter the priesthood. Desme was recently selected the 2009 Arizona Fall League MVP and was considered one of the top prospects in Oakland's system. "We respect Grant's decision and wish him nothing but the best in his future endeavors," A's general manager Billy Beane said in a statement. The 23-year-old outfielder batted .288 with 31 homers, 89 RBIs and 40 stolen bases in 131 games at Class-A Kane County and Stockton last season.

It's unclear whether Beane considered Desme's VORP (Value Over Replacement Priest) when the A's drafted him.