Given Matsui's performance in the Yankees' 3-1 World Series-evening win in Game 2 on Thursday night, Girardi is running out of reasons not to, bad knees and all.
On a night when familiar foe Pedro Martinez pitched Derek Jeter, Johnny Damon and Alex Rodriguez to a combined 1-for-12 with seven strikeouts, it was Matsui who blasted the decisive homer, a two-out sixth-inning shot that traveled an estimated 320 feet.
Down in the count 1-2, Matsui took the second consecutive curveball he saw over the right-field fence, sending the crowd of 50,181 at the new Yankee Stadium to its feet in a jolt of fervor.
"What can you say about him?" Yankees captain Derek Jeter said. "He's a guy you want to see up in big situations, because you know he's going to give a good at-bat. And he hit a huge home run for us."
Matsui's homer was a game-changer, allowing Girardi to hand the ball to Mariano Rivera for the first time this series. The All-Star closer collected the game's final six outs to preserve the win and even the series at one apiece before the Yankees travel to Philadelphia for Saturday's Game 3.
In a series where Phillies pitching has handcuffed the Yankees' high-octane offense to three runs (two earned) through the first 18 innings, Matsui is 3-for-6 with a homer and walk, a .500 average New York can't afford to lose.
"That's something we're going to have to talk about," Girardi said of using the 35-year-old Matsui in the outfield for the first time this season. "We'll see how he's doing. We'll have to see. We'll make a decision when we get there. We have all day to think about it [during Friday's off-day.]"
"It's not really my decision," Matsui said through an interpreter. "If the manager decides to put me in the outfield, then I'm going to make sure that I am ready for that."
Matsui has had fluid in his surgically repaired left knee drained several times this season, and he was plagued by right knee woes during his career in Japan. As the Yankees' designated hitter for 142 games this season, he hit .274 with 28 homers and 90 RBIs.
Thursday's eventual game-winning homer was Matsui's second blast of the postseason dating back to Game 1 of the American League Division Series. Mastsui connected for a two-run homer off Twins pitcher Francisco Liriano in the fifth inning of the Yankees' 7-2 win.
"Matsui is a professional, he comes [in], he's ready to play every day," Jeter said. "He can hit home runs, moves the ball the other way, he's great with guys on base. He comes to play. He wants to win [and] he's one of my favorite teammates."
Brittany Ghiroli is a contributor to MLB.com This story was not subject to the approval of Major League Baseball or its clubs.