The oldest winning pitcher in Nippon Professional Baseball history, Masahiro Yamamoto worked a season-high 5⅔ innings in the minors on Wednesday as he builds toward making his first-team season debut.

Yamamoto, who will turn 50 next month, allowed just four hits in the Chunichi Dragons' game against the Western League powerhouse Fukuoka Softbank Hawks at Nagoya Stadium.

"As far as results go, I'm glad I kept them off the board. I've been doing well," said Yamamoto, who was the Dragons' fifth-round draft pick out of high school in 1983 and has a career 219-165 record with the Central League club.

Last September, Yamamoto rewrote NPB's record as the oldest winning pitcher, surpassing the mark set by Hall of Famer Shinji Hamazaki in 1950, when he won as a reliever at the age of 48 years, four months. The major league record for the oldest pitcher to win a game was set in 2012 by 49-year-old lefty Jamie Moyer.

Yamamoto was able to locate his curve ball and get batters to hit his pitches. In his previous start, he threw five scoreless innings.

"What good would it do to be satisfied with this," he said. "I am working toward raising my game enough that they will call for me to join the first team."

Dragons ace Kazuki Yoshimi, who is rehabbing on the farm, pitched in his first game since being deactivated in May with right-elbow stiffness, retiring all six batters he faced over two perfect innings.

Yoshimi, who is coming back from Tommy John elbow surgery, is 3-0 this season in seven starts with a 0.84 earned run average.