The San Francisco 49ers are 5-0 after winning just four games last season.
Over the last two weeks, the 49ers' defense has allowed just 10 points and 345 total yards in wins over the Cleveland Browns and Los Angeles Rams.
"I'm very happy with how we played," Shanahan said. "We're 5-0, which is a great thing, but we're not playing our best ball. We can do a lot of things better than that. It seemed like our defense played at an extremely high level, obviously minus the first drive. We can continue to get better on offense. We can continue to get better on special teams. I also think our defense is just getting started, too."
Only the New England Patriots are allowing fewer yards per game than the 49ers.