A day after celebrating his 40th birthday with a goal, Kawasaki Frontale stalwart Kengo Nakamura on Sunday announced he will retire at the end of the J-League season.

Kengo Nakamura of Kawasaki Frontale on Oct. 31, 2020. (Kyodo)  

The former Japan midfielder became the league's oldest-ever Player of the Year in 2016 at age 36. He helped Kawasaki win their first title in 2017 and go back-to-back the following year.

"I've been able to hang in for the past five years because I had already decided to retire (at 40). There wasn't a shadow of a doubt," Nakamura said during an online press conference.

A member of the Samurai Blue squad that reached the last 16 at the 2010 World Cup in South Africa, Nakamura has spent his entire professional career with Kawasaki, joining the then second-division club out of Chuo University in 2003.

The Tokyo native badly injured his left knee last November and returned in August, scoring a goal in his comeback game, a 5-0 rout of Shimizu S-Pulse.

Nakamura scored the winner Saturday as Kawasaki, the runaway leaders in the J-League top flight, beat visiting FC Tokyo 2-1 for their 12th straight victory.

"The decision (to retire) has nothing to do with the injury," he said. "I want to play in games until the end, enjoying my remaining days and not wasting any of them."

Nakamura has 74 goals in 463 appearances in the J1. He scored six goals in 68 appearances for Japan.