Milwaukee Brewers first baseman Corey Hart underwent surgery Friday morning on his injured right knee. Earlier in the week, Hart said he hoped to postpone surgery while he sought a second opinion, holding on to the possibility of rehabbing the knee and playing through the injury this season. But the Brewers announced that Dr. William Raasch went ahead with the surgery, which involved debriding the knee joint surface and repairing a small meniscal tear. The estimated recovery time is three to four months. Hart, 30, is coming off a strong 2012 season when he hit .270 with 30 homers and 83 RBI. His replacement at first base is expected to be Mat Gamel.