"That's a matchup I would pay to see, and I hope the ballpark is packed, because I think that's going to be a dandy," McClendon said before the Yankees switched up their plans for the 7:10 p.m. PT series opener.
Iwakuma and Tanaka were teammates with the Rakuten Golden Eagles from 2007-11 during Iwakuma's last five years in Japan. Iwakuma is eight years older, at 33, and he helped groom Tanaka as the phenom was just getting started in professional ball. So the Mariners standout was eager as well about the expected duel.
"We've always been on the same side until a couple years ago," Iwakuma said through translator Antony Suzuki. "You look at him and he's a teammate, he was part of the family. You used to root for the guy, and now you're going against him."
Instead, Iwakuma will face Vidal Nuno, with Tanaka going Wednesday against Chris Young.
Tanaka is 9-1 with a 2.02 ERA in his rookie season with the Yankees, as the 25-year-old has done nothing to disappoint after signing a seven-year, $155 million deal. Iwakuma isn't as big a name nationally, and he is pitching the second year of a two-year, $14 million deal that includes another option year at $7 million for 2015. But Iwakuma has been just as effective in the Major Leagues in his three seasons in Seattle.
After missing the first month of this season with a torn finger tendon, Iwakuma has gone 4-2 with a 2.66 ERA. In 56 career starts with Seattle, he's posted a 27-13 record and a 2.82 ERA, and he finished third in last year's American League Cy Young Award voting.
Iwakuma said the two have a good friendship and will likely have dinner later in the week. But they aren't on the same team anymore, so does Iwakuma have any batting hints for his teammates when they face Tanaka for the first time?
"I do have some tips," Iwakuma said with a smile, "but that's top secret."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.