FBO: Number Crunching, Week 4

Let's get ready for the battle of Philly past and Philly present. US Presswire

Each week, Football Outsiders takes a look at every game on the NFL schedule with a mix of interesting numbers and in-depth statistical analysis. Much of the analysis is based on DVOA (defense-adjusted value over average), which takes every single play during the season and compares it to the league average based on situation and opponent. DVOA and Football Outsiders' other advanced stats are explained here. Since it is still early in the regular season, this week's notes are a mix of 2009 and 2010 statistics. Remember that 2010 numbers are based on a very small sample size and do not include opponent adjustments.

All times listed below are ET.

Sunday 1 p.m. games

San Francisco 49ers at Atlanta Falcons (FOX)
The Falcons' defense ranks 28th in the league in DVOA on first downs, but they get better with each passing down. On second down, they're 15th, and on third downs, they're second-best in the league. As the weeks go along, their performance on first downs will likely improve, but their performance on third downs should be expected to slip.

A year ago, the 49ers had the second-best red zone defense in football. This year, they have the fourth-worst DVOA of any defense inside their own 20.