Yamamoto (triceps) could begin a rehab assignment Wednesday, David Vassegh of AM 570 LA Sports reports.
Yamamoto has been eyeing a mid-September return and will advance to a minor-league rehab assignment next week if his next bullpen session goes well. The right-hander has been sidelined since June 15 and is expected to throw three simulated innings in the bullpen session. He'll likely require multiple rehab starts before being activated from the 60-day injured list.