What is being called NFL's best rivalry right now will once again commence this Sunday in a game between the Seattle Seahawks and the San Francisco 49ers.

The coaches of these two teams, Pete Carroll (SEA) and Jim Harbaugh (SF), have a history that goes way back to when they coached against each other in the Pac-10. It all began when Harbaugh was coaching at Stanford and Carroll at USC, and Harbaugh made a comment about Carroll leaving after the next season. Carroll did not take this very well.

Harbaugh only made it worse in his next press conference when asked about his comment, and he stood by it. That was in 2007. According to Seattletimes.com, In 2009 Stanford upset USC at the Coliseum 55-21. Harbaugh went for 2 points late in the game, and once the game ended the two coaches met at midfield for the post game handshake. This is when it really started:

Carroll:"What's your deal? You alright?"

Harbaugh: "Yea, I'm great. What's your deal?"

Carroll: "Nice game."

Sports Illustrated reports that although the two coaches have their differences, they preach the same brand of football. Play defense, run the ball well, and limit mistakes.

These two smash mouth football teams go head to head on Sunday Night Football in what should be a thrilling chapter in a bitter rivalry.