Giants’ Affeldt to announce retirement

Relief pitcher Jeremy Affeldt, one of the longest-tenured Giants who who made his mark on the field with his postseasons successes and off the field with his advocacy work, will announce his retirement from baseball Thursday morning, the Giants said.

Affeldt, 36, has been a major-leaguer for 14 seasons and a Giant since 2009, one of the “Core Four” of relief pitchers that has been together through the three World Series championship runs, along with Javier Lopez, Sergio Romo and Santiago Casilla.

Beset by injuries this year, the left-hander struggled to a 6.09 ERA in 50 games this season. But at his best he was a superb groundball known for his ability to pitch multiple innings with success…