No, not Iwakuma becoming just the second Japanese pitcher to throw a no-hitter in Major League Baseball - as important an accomplishment as that was - joining Hideo Nomo in exclusive company when he shut down the Baltimore Orioles on Wednesday.
That ended the run of 12 straight no-hitters - 11 individual and one combined - thrown by National League pitchers. Almost three years to the day that teammate Felix Hernandez threw a perfect game against the Tampa Bay Rays, Iwakuma finally ended the drought for the American League.
It's a rare stat and in many ways likely just an odd coincidence. But it also highlights the difficulty of pitching in the American League, where there simply are no free outs thanks to the designated hitter.
''I think the outs are tougher. Look, the lineups are deeper. The DH's in the American League, the DH's are animals,'' Seattle manager Lloyd McClendon said. ''Those are tough outs. There really are no easy outs in the American League.''
Four of the last five no-hitters in American League ballparks have come at Safeco Field. Prior to Hernandez's perfect game, six Seattle pitchers combined on a no-hitter in June 2012 against the Los Angeles Dodgers and unknown Phillip Humber threw a perfect game for the Chicago White Sox against the Mariners that April.
The NL streak was the longest streak of no-hitters in one league since the inception of the AL in 1901.
''There's an obvious number one reason. That reason and probably just coincidence,'' Texas manager Jeff Banister said Thursday. ''I've got to believe that an oddsmaker would say that it's a little more challenging in our league. They are still pretty special, no matter what the circumstance or situation is. That's why we celebrate them so much.''
Iwakuma was as unlikely a candidate as any to throw the fourth no-hitter of this season. He spent 2 1/2 months on the disabled list after straining a muscle in his back and side in late April, another in a series of injuries that has made his career in the majors go in fits and starts.
He had pitched more than eight innings only twice in his career before Wednesday and had never pitched a complete game. He came close earlier this month against Minnesota, throwing 8 2-3 innings before being lifted in a game that went to extra innings.
''I couldn't help my team at all and that's all I had in mind, to come back and give it all I've got every start and make up for the lost time I've had the first half and do anything to contribute for the team,'' Iwakuma said through an interpreter.
Iwakuma is the 17th pitcher since 1914 to have his first career complete game be a no-hitter and the first since Humber's unlikely perfect game. McClendon would have picked Hernandez - obviously - and young right-hander Taijuan Walker as more likely candidates on his staff to throw a no-hitter.
''I said about three weeks ago the `Bear' was back and he's only getting better,'' McClendon said. ''It's nice to see because I think this is probably the longest stretch I've had him where he's been truly healthy and the ball is coming out and the velocity is back. He can work down in the zone, he can elevate the fastball. That's what makes him special.''
AP Sports Writer Dave Campbell contributed to this report.