Red Sox manager Bobby Valentine addressed the report before Wednesday night's game against the Kansas City Royals.
"I haven't talked to Josh about this yet, so I'm not sure I can really comment on it other than I can say physical issues, I guess, he had a sore lat," Valentine said. "He wasn't an injured player. I know that. And we'll take it from there. But I'm sure Josh wouldn't do anything that's going to jeopardize his team or his season. I know that."
Beckett flew back to Boston on Wednesday and was unavailable to meet with the media. He is scheduled to start on Thursday.
According to the report, teammate Clay Buchholz was golfing with Beckett on Boston's off day. Buchholz declined to comment before Wednesday's game.
Beckett hasn't pitched since April 29, when he threw 126 pitches against Chicago. Last Wednesday, the day before Beckett reportedly was spotted on the links, Valentine announced the right-hander would miss his start -- scheduled for Saturday -- with stiffness in his lat muscle. Beckett later admitted that the injury existed before the start against the White Sox.
When asked about the report during his appearance Wednesday on WEEI sports radio in Boston, Valentine said he'd heard about it but seemed undecided on how to handle it.
"I'm aware of the story being out there. ... No, I haven't gotten to Josh about that yet and I'm trying to sort out my feelings," he said. "Golf is as much a part of the pitching culture as a curveball; I know that for sure."
Valentine told WEEI he wouldn't comment further until he received more information, but noted that Beckett hadn't been shut down with an injury but was merely missing a start because of the tightness.
"When we decided for Josh not to make his start, it wasn't because he was injured," Valentine said. "It was a precautionary situation because his lat was a little tight."
But he indicated he wouldn't condone his pitcher playing a full round of golf if he's trying to rest.
"Again, I don't know the specifics of the situation," Valentine said. "I don't know if he was out at a charity match, just putting, or if he was whaling away and felt that might have loosened things up. I have no idea what the situation actually is, so it's hard for me to comment on it. ... If that was the case (that he played golf), I would say that was less than the best thing to do on that day off."
ESPNBoston.com contributor Jayson Jenks provided information to this report.