Hiroshi Tanahashi's nickname in NJPW was The Ace. The Ace was given to him as he was one of the top stars in the promotion and was one of the most popular wrestlers in the world. The nickname was used to describe Tanahashi's status as one of the best wrestlers in the world and his ability to draw large crowds.
The Prime Ace: Test Your Knowledge on Hiroshi Tanahashi, the Wrestling Phenomenon!