Moncada was rated as baseball's No. 1 prospect, per MLB.com.
The Cuban second and third baseman signed with the Red Sox as an international free agent in March 2015. He earned a record $31.5 million signing bonus at age 20 and was not considered to be Major League ready until 2018 or later.
Now 21, Moncada will be skipping Triple-A with the promotion. In 486 plate appearances between Class-A Advanced Salem and Double-A Portland, he has hit for a .298/.411/.518 slash line this season, adding 15 home runs, 61 RBI and 45 stolen bases.
A switch-hitter, Moncada is expected to help out at third base with Boston, who currently is platooning Aaron Hill and Travis Shaw there. Neither player in the current platoon has posted great numbers there offensively.
Moncada will also help out on the bases for the Red Sox and could add potentially game-changing speed late in ballgames.
In fact, MLB.com rates Moncada's best tool as his speed, which is given a 65 on the 20-80 scale. A great all-around player, Moncada already grades out as a 65 overall, which is considered above Major league average.
Moncada has drawn comparisons to Mariners second baseman Robinson Cano, though he adds more speed to his game.