It will be interesting to see if his fastball works in the majors and in particular if he can sustain the level he throws at. 93 mph isn't all that much and if the bigger ball hinders his ability to throw at that level there could be problems.
I really think he'll bust out. Another pitcher the Yanks will regret giving that kind of contract to.
Time will tell, but the Yankees really needed to make this move. I think the most questionable move they've made this offseason is signing Beltran. That just felt so reactionary to the Cano signing...and it just crowded the outfield even more. Hopefully Beltran has a huge year...but at his age, it doesn't seem likely.
The pitching staff needed a jolt though. Just this offseason the team lost Rivera, Pettitte, Hughes, Chamberlain, and Boone Logan. They've got Sabathia, Kuroda, and Nova...and then after that, it gets questionable very quickly. They still have no idea what they've got with Michael Pineda (most likely nothing)...but they had to roll the dice somewhere. And the young Steinbrenners really needed to show the fans that missing the playoffs isn't something to get used to. If they didn't spend this money...they would lose it when people stop showing up at the ballpark.
Even if Tanaka doesn't become an ace...it's not like the Yanks had no reason for signing him. Several teams were going after him. There had to be a reason for that.