What happened: San Francisco joins Indianapolis from 2005 and Miami entries from 1984 and 1989 on the zero-sacks list. Miami's 1989 entry extended the run through five games.

Why it matters: Clean protection limits drive-killing losses and keeps the offense on schedule. Matching groups separated by decades shows how seldom lines start this cleanly.

What to watch: What to watch is whether San Francisco carries the streak into game five.