Oakland Athletics starting pitcher Marco Estrada underwent a minimally-invasive ablation procedure on his back on Tuesday after he was still experiencing pain from his lumbar strain. He will obviously need more than the 10 days on the injured list before he returns. The procedure uses radio-frequency waves to provide relief for chronic back pain. The right-hander will be shut down from all baseball activities for the next seven days, and there is no timetable for his return. Estrada is 0-2 with[...]