"I think he went about it the right way in Spring Training, but now the time comes where you just throw the ball the way you're capable and all the rest of it is kind of put to the wayside," Rothschild said.
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The Yankees have lined Tanaka up to start on April 4 against the Astros at Yankee Stadium, and manager Joe Girardi said Tanaka's next outing -- expected to be on Tuesday against the Pirates -- will be viewed as a crucial springboard into the season.
"His next start obviously is really important, because you want players to feel good about themselves going into the season," Girardi said. "He's got a big week of work ahead of him to get going."
Prior to Wednesday's start, Rothschild said he and Tanaka spoke about better executing the fastball to different areas, especially down and away from hitters. Rothschild said Tanaka's slider has been a good pitch for him most of the spring, but not on Wednesday.
"Last spring it was all the talk about his velocity and everything else, so there's always questions about everybody during the course of a season or spring," Rothschild said. "Would I like to see him get things together? Yes."
Rothschild said he plans to speak to Tanaka again this week, and he believes the adjustments that Tanaka needs to make will be "fairly subtle."
"The adjustment I want to make is he just goes back to throwing the ball and trusting it," Rothschild said. "That mechanically he's OK and away from thinking about mechanics. ... I think you could equate it to dancing; if you're thinking about it, it probably doesn't look good."
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.