The A's have begun extended spring training in Arizona, but highly touted Dominican right-hander Michael Ynoa has yet to arrive. Ynoa was signed to a $4.25M signing bonus. David Forst, Oakland's assistant GM, said the A's will carefully monitor the workload of Ynoa, a 17-year-old considered the best prospect in Latin America when Oakland signed him last summer. Ynoa likely will join the A's Phoenix-based rookie league team after he arrives in the United States. The A's want him to be fresh when the fall Instructional League begins in September.