Mata was promoted to Double-A Portland on Monday, Alex Speier of The Boston Globe reports.
Mata spent a month on the injured list with a right shoulder strain, but when healthy this season he's been lights out for High-A Salem with a 1.75 ERA, 1.09 WHIP and 52:10 K:BB in 10 starts. The 20-year-old has shown in the lower minors why he's a highly-touted prospect, and he's likely to remain at Portland for the second half of the season.