As new neighbor David Robertson joked, it wasn't as though Rivera usually showed up at camp this early anyway, so the locker might as well go to use.
The assignment is an indication of how highly the Yankees think of Tanaka, 25, who signed a seven-year, $155 million contract in January after a standout career in Japan.
That locker also figures to be a popular destination this spring for media members as Tanaka begins a series of adjustments in preparation for his first Major League season.
Tanaka said that the biggest adjustment will be getting used to pitching every fifth day instead of once a week, as he did in Japan, but that he is ready to make whatever changes the coaching staff suggests.
"I do want to learn the way to do it over here," he said. "I'm not really looking to just go about my way and do it in the Japanese way that I've been doing. Basically, I'll try to get some advice, learn the way it's done here and go about it."
Tanaka shared his thoughts during a pair of large group interviews outside the clubhouse on Friday morning, surrounded by TV cameras and microphones. A major star in Japan, he did not seem affected by the spotlight.
"I do feel very honored to get all this attention," he said. "Basically, what I need to do is to go out there and perform. That's what I'm intending to do."
Tanaka was able to greet several of his new teammates on Friday, including Hiroki Kuroda.
"He told me, 'Just be yourself. Try not to do too much, do your own pace, and you should be OK,'" Tanaka said.
New catcher Brian McCann received an iPad from the club that was loaded with all of Tanaka's starts last season for the Tohoku Rakuten Golden Eagles. McCann was impressed by the video and looks forward to seeing Tanaka in person.
"It was spot on with what I've heard," McCann said. "The guy can pretty much do whatever he wants with a baseball, which is pretty amazing. His split is as good as it gets; pitches inside, outside, really knows what he's doing. So I'm excited to get to know him, excited to catch him."
Tanaka played catch in the outfield on Friday, and he is scheduled to throw a bullpen on Saturday, his second in Florida after tossing about 25 pitches off the mound to Francisco Cervelli at the Minor League complex on Thursday.
"I'm feeling pretty good," Tanaka said. "The bullpen [on Thursday] was actually the first time I had the catcher sit down and throw, but for the first time, I feel it went pretty good."