But Iwakuma, one of five pending free agents on the Mariners roster, declined to offer any hints as to his future after wrapping up a 9-5 season with a 3.16 ERA.
"I didn't try to think anything of it. I just wanted to finish up," Iwakuma said through interpreter Daisuke Sekiba. "What's going to happen next, I'll think about later."
The Mariners certainly liked what they saw from Iwakuma, who went 8-4 with a 2.65 ERA in 16 starts after moving into the rotation in midseason. His ERA was the lowest as a rookie in club history for anyone making 10 or more starts, edging the 2.67 of Felix Hernandez in 2005.
Iwakuma obviously isn't your normal rookie, having been a standout in Japan for the past decade. But he was new to the Majors and it took time to adjust, which is why his initial time in the bullpen this season paid off in the long run.
"I learned a lot of things, physically how to pitch against hitters and afterward as I became a starter I got good experience because of the bullpen pitching," he said. "There's nothing different between the pitching, but the hitters have more power here than Japanese players."
And what did he learn about facing those power hitters?
"Don't pitch the cookies," Iwakuma said. "They're going to hit home runs, so I try to think about how to pitch to them."
His overall thoughts on his first season in the Majors?
"I'm very happy for the year," he said. "I finished up strong, so I feel very happy now."
The team's other pending free agents are catcher Miguel Olivo and pitchers Kevin Millwood, Oliver Perez and George Sherrill. Olivo has a club option for 2013, but isn't expecting to return. Millwood is pondering retirement, Sherrill is coming off Tommy John surgery and Perez had a nice comeback season as a reliever this year on a Minor League deal.