The Mariners announced that Hisashi Iwakuma’s $7MM option has officially vested based on his on-field performance. The option was widely believed to be a club option, however Bob Dutton of the Tacoma News Tribune recently reported that the option vested by virtue of Iwakuma’s on-field performance. The Mariners have now officially announced as much.

Retaining Iwakuma for a mere $7MM would have been a no-brainer regardless, as the 33-year-old again enjoyed another strong season with the Mariners. In his third big league season, the Japanese righty totaled a 3.52 ERA with 7.7. K/9, 1.1 BB/9 and a 50.2 percent ground-ball rate in 179 innings of work. The somewhat diminished innings total is the result of a strained tendon in his middle finger that kept him on the disabled list through the month of April. He debuted on May 3, however, and made each of his starts for the remainder of the season.

Iwakuma has been an exceptional find for the Mariners, who initially signed him for just $1.5MM one year after the A’s failed to work out a contract with him following their submission of a $19.1MM bid for his exclusive negotiating rights (that sum was returned to Oakland when a deal was not reached). Following a rookie campaign that was split between the bullpen and the rotation, Iwakuma signed a two-year, $14MM extension which contained this option. He then broke out in 2013 with an elite season that led to a third-place finish in the AL Cy Young voting.

All told, Iwakuma owns a stellar 3.07 ERA with 7.6 K/9, 1.8 BB/9 and a 50.1 percent ground-ball rate in 524 big league innings since leaving the Rakuten Golden Eagles of Nippon Professional Baseball for the Major Leagues. Fangraphs pegs his career value at 7.7 wins above replacement, while Baseball-Reference (11.5) and RA9-WAR (12.3) are significantly more bullish.