SANTA CLARA, Calif. -- An examination of four hot issues from the San Francisco 49ers' 34-3 win against the Texans:Another defensive injury: The 49ers defense potentially suffered another key loss when standout defensive tackle Ray McDonald went out with a right biceps injury. McDonald said after the game that he felt a sting and is concerned. He will have an MRI on Monday. Tony Jerod-Eddie replaced McDonald. The 49ers defense has suffered several injuries, and has played the past two games without All-Pro linebackers Aldon Smith (receiving treatment for alcohol abuse) and Patrick Willis (groin).