49ers linebacker Patrick Willis "could miss a little time" with a Grade II hamstring strain, according to a league source. His status for Sunday's game at Arizona is unclear. "Nothing to share," coach Jim Harbaugh said. "I'm not in Patrick's body. It's hard to say with any injury, including a hamstring. ... I guess I was more relieved that it wasn't a knee. That area that they were working on -- I was concerned about that, for Patrick and for our team."