SAN FRANCISCO — Now that his season is over, Matt Chapman can admit that most of it was spent in discomfort. The Giants third baseman said Saturday that his core muscle problems started in Cincinnati back in mid-April, although he was able to manage them for a few months. Chapman finally went on the IL on July 1, and when he seemed to be nearing a return around the trade deadline, things still didn’t quite feel right. He had surgery earlier this week, ending his season but also giving him clarity on what exactly was wrong.

Chapman said a core muscle was partially ripped off his pubic bone on both sides and had to be reattached. He was able to get enough treatment before games to mostly feel like his usual self, but it progressively got worse.

“I would feel it every day but I would get warmed up and to a spot where I could still play,” he said. “And I thought I could still play. It’s not really an excuse — guys are always dealing with stuff throughout the year and I think it got progressively worse probably every day, but it never was at a point where I wanted to come out.

“I figured I could play...