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The hiring of Kiffin means the Cowboys will switch back to the 4-3 defense after going to the 3-4 under Bill Parcells in 2005. The most notable switch will be Pro Bowl linebacker DeMarcus Ware becoming a defensive end, and Anthony Spencer could make the same move if the Cowboys re-sign him.
At Tampa, Kiffin's defenses frequently were among the league's best, and the Buccaneers won the Super Bowl with him after the 2002 season. That unit was the first in the league since the champion Chicago Bears in 1985 to lead the NFL in total defense, points allowed and interceptions.
Ryan was fired Tuesday after two seasons. His defenses were inconsistent pressuring the quarterback and didn't force many turnovers. In 2011, the Cowboys allowed the second-most passing yards in franchise history. This season's injury-plagued unit couldn't stop New Orleans quarterback Drew Brees and rookie Washington running back Alfred Morris in season-ending losses that kept Dallas out of the playoffs for the third straight year.
Jones also said in a taped interview being aired this weekend that he wasn't pleased with some of the early-season performances before key defenders started getting hurt. Garrett said in a statement announcing the firing of Ryan that the team was going in a different philosophical direction.
The Buccaneers finished in the top 10 in total defense 11 times in 13 years under Kiffin and had streaks of 69 straight games with a sack and 54 with at least one turnover during that stretch. Tampa had 31 interceptions the year it won the Super Bowl, nine more than the Cowboys have the past two seasons combined.
Kiffin turns 73 next month.