Masayoshi Amamiya is viewed as so essential to operations at the Bank of Japan that he's known inside the central bank as "Mr. BOJ."

With the shift in recent months from a blitz on deflation to a long-haul campaign that's set to outlast Gov. Haruhiko Kuroda's term, Amamiya is at the fore of managing interest rates and nudging consumer prices toward the BOJ's distant 2 percent inflation goal.

The 61-year-old could also be among contenders in early 2018, when the government of Prime Minister Shinzo Abe considers replacements for Kuroda, 72, and his two deputy governors.