Nuno is winless in eight starts at Yankee Stadium, while Tanaka leads the Majors in wins (11) and the American League in ERA (2.11), but Girardi nevertheless selected Nuno to face the Red Sox on Friday in the opener of a three-game series.
Girardi outlined his logic behind the decision before the game.
Tanaka, still in his first season in the Majors, was used to throwing once every seven days in Japan. The Yankees are beginning a stretch of 17 consecutive games without an off-day until the All-Star break, so Girardi wanted to give him an extra day of rest while he could.
And the rest of the Yankees' rotation could benefit from a break.
As Girardi pointed out, Chase Whitley is a rookie in his first season in the Majors. Hiroki Kuroda may have suffered from fatigue toward the end of last season. David Phelps has been used in both the rotation and bullpen throughout his career and has never thrown more than 100 innings in the Majors.
"I have to be careful, it's a long season," Girardi said. "And if I start [Tanaka] today or tomorrow, he still makes the same number of starts before the All-Star [break]. This is about five guys, it's not about one guy."
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch and read his MLBlog, Bombers Beat. Jamal Collier is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.