Daisuke Matsuzaka, who has been rehabbing since a fan injured him with an overzealous high five during spring training in February, apologized on Friday for playing golf the day before.

The Chunichi Dragons indicated Thursday that the former Boston Red Sox and New York Mets pitcher would face a penalty for breaking team rules, which got his former Japan teammate Yu Darvish up in arms about Japanese baseball’s repressive customs.

“I made trouble through my careless acts,” Matsuzaka told reporters at Nagoya Stadium, where he rejoined the Dragons farm team after a trip to the Tokyo area for treatment.

The team prohibits players from playing golf on practice days, even though Matsuzaka was not scheduled to join his teammates in their practice over 200 miles away in Nagoya.

On Monday, Matsuzaka threw his first bullpen since February, and was slated this week to throw batting practice. “I need to refocus and concentrate on baseball,” he said.

“I will give my best effort so I can contribute to the team as soon as possible.”

Injured and rehabbing players in Japan are expected to be monk-like in their devotion to “returning to the team as soon as possible.” And clubs typically do not make such players available for interviews regardless of their actual availability.

Yu Darvish hit out at the custom on Twitter.

“Of course, it would be no good if he lied to the team and skipped out on his treatment to play golf, but nobody was writing that. But playing golf either before or after his treatment is no big deal. Simply put, the restrictions placed on injured players in Japan are oppressive.”

Chicago Cubs pitcher Yu Darvish via Twitter on the subject of rehabbing pitcher Daisuke Matsuzaka being punished for playing golf.