As MLBTR reported at the time of the signing, Mijares' deal included an March opt out clause that he could trigger if he did not like his prospects in Boston. Had things worked out, the 29-year-old would have earned $1MM on the major league roster with another possible $1MM tied to games pitched.
Mijares spent last season with the Giants and even though his 4.22 ERA in 49 innings was the second-highest of his career, his rate statistics (9.9 K/9 and 3.7 BB/9) were strong. Unfortunately, the left-hander suffered from a staggering .410 BABIP, the highest mark in all of baseball among pitchers with at least 40 innings. Advanced metrics like FIP (3.05), xFIP (3.90), and SIERA (3.45) indicated that Mijares outperformed his ERA last year.