Tedy Bruschi's defensive index

When judging total defense in the NFL, many often point to yards allowed as the primary measure for a unit’s effectiveness. ESPN analyst Tedy Bruschi sees that as a flawed analysis.

Bruschi instead has put together his own formula, averaging what he views as the four key statistics: points allowed (only on defense, not including pick-sixes or special-teams scores), red zone defense (measured by percentage of touchdowns allowed versus total trips), third-down percentage and total turnovers (created solely by the defense, not including special teams).

What results, with an assist from Jason Vida of ESPN’s Stats & Information department, is the “Bruschi defensive index.” Some thoughts on this week’s index include:

• If the New England Patriots can't find a way to get off the field on third down, it will end their season. For this offense to score points they will need as many possessions as possible. If teams continue to convert on third down, it will keep Tom Brady and the offense off the field. Especially if the defense continues to fall in their turnover rankings.

• Don't assume the Philadelphia Eagles are all about offense. They've gotten better as the year has progressed and are strong in the red area and taking the ball away.

• The Tampa Bay Buccaneers, at 4-9, are the only team with a losing record in the Top 10.