Moncada, a Cuban defector widely regarded as Boston's top prospect, had been working out in Florida at extended spring training. He is expected to play second base but can also play third base and the outfield.
Moncada, who turns 20 later this month, was signed in February for $31.5 million, the largest signing bonus ever paid to an amateur free agent. The signing will cost the Red Sox $63 million because they will be taxed by MLB for exceeding their allotted international amateur free agent funds.
"He did as well as expected with his transition on and off the field -- a hard worker and eager to learn,'' Red Sox director of player development Ben Crockett told ESPN.com in an email Sunday.
Before arriving at spring training, Moncada had not played organized baseball since leaving Cuba late in 2013.
- Dan Gartland