The M's extended the right-hander, who will avoid free agency with the signing to remain in Seattle.
Time was of the essence as the Seattle Mariners reached a two-year contract extension with right-handed pitcher Hisashi Iwakuma that includes a 2015 option. Financial terms of the deal were not made available.
If the Mariners had not reached an agreement with him by Saturday, the Japanese hurler would have become a free agent and would not be eligible to play for Seattle until May 2013.
Iwakuma was signed as a free agent from Japan prior to the 2012 season and figures to be an important key to the rotation over the life of his contract. The 31-year-old was 9-5 with a 3.16 ERA in 30 appearances last year. In 16 starts, he was 8-4 and had a 2.65 ERA. He also recorded two saves.
Most notably, he had a stellar 6-2 record with a 1.83 ERA in his last nine starts and added 43 strikeouts over that stretch. He set a Mariners' rookie record with 13 strikeouts against the Toronto Blue Jays on Jul. 30.