Chunichi Dragons veteran left-hander Masahiro Yamamoto had to leave the mound after throwing just one pitch in a farm league game at Nagoya Dome on Tuesday.
The 49-year-old Yamamoto, who last September became the oldest pitcher to win a game in Japanese baseball history, said he heard his right knee pop. He was pitching in his first preseason game in a Western League spring development matchup against the Fukuoka Softbank Hawks.
"My knee popped. I can walk so I don't think it's anything serious. Might be a sprain," Yamamoto said after the game before heading for a hospital.
There were no abnormalities found in the team trainer's examination.
"There were indentations made by the two (previous) pitchers' feet (where the right foot landed)," said Yamamoto, who left after throwing one pitch to the leadoff man in the fourth inning.
"It was my carelessness. My power in a game is different. I'll have a little setback in my preparations, but I'll do my best. I'll be here (at the stadium) tomorrow."