Tanaka started on Thursday for the RailRiders, throwing three scoreless innings against Durham. He permitted two hits with no walks and two strikeouts, tossing 25 of 41 pitches for strikes.
"He feels good about it. He says he feels good today, his arm feels great," Girardi said. "He wants to be able to throw more sliders, curveballs -- that sort of thing. When you throw 41 pitches, a lot of times you don't get a chance to work on it much."
It is possible that Tanaka could need just two Minor League rehab starts before returning to the big league rotation. Girardi said that the Yankees are following a normal rehab protocol with Tanaka, considering that he was built up and made four big league starts in April.
The Yanks are giving Tanaka an extra day of rest between Minor League starts, and that could continue in the near future; Girardi said they would "play it by ear."
Should Tanaka's pitch count see a similar jump after the scheduled 65-pitch start at Pawtucket, Girardi said that the Yanks may consider having him use those 80 or more pitches at the big league level rather than against a Minor League lineup.
"I think the one thing that you have to do is you have to evaluate each start he makes and how crisp the stuff is, and then decide if he's not a 100-pitch pitcher. Can your club handle that?" Girardi said. "Have we done that before? Yes. But I think we'll continue to evaluate where we think he's at and we'll make a decision."
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch, on Facebook and read his MLBlog, Bombers Beat. This story was not subject to the approval of Major League Baseball or its clubs.