Patriots banking on Tom Brady until he's 40

Tom Brady has said for years that he wants to play until he's 40 years old. It's an unusual goal in the NFL, but at 35 Brady is still playing at an elite level and appears to have a shot.

It's clear the New England Patriots also think Brady is capable of making it to the big 4-0. Peter King of Sports Illustrated reports New England agreed to a three-year, $27 million contract extension that ensures Brady will retire a Patriot. Health permitting, Brady will be under center in New England through the 2017 season, which is after his 40th birthday.

The Patriots are taking a calculated risk with Brady. He will be 36 at the start of this season. With the exception of a season-ending knee injury in 2008, Brady has been in great health most of his career. But injuries can take a toll at any point. The older Brady gets, the more difficult it is for his body to take the weekly punishment, and New England has contracturally committed to Brady for five more seasons.

But the extension also gives New England salary-cap flexibility. Brady reportedly reduced his current cap number and signed for a below-market value of $9 million per season in the final three years of the contract. That allows the Patriots to chase other free agents and remain in playoff contention for years to come.

Brady didn't show any signs of slowing down this past season. He received MVP consideration in 2012 after throwing for 4,827 yards, 34 touchdowns and just eight interceptions. Brady led the Patriots to the AFC title game for the second straight year, where they lost to the eventual Super Bowl champion Baltimore Ravens.

The Patriots' title window remains open as long as Brady is healthy and upright. Signing a 35-year old to a three-year contract extension can be risky in the NFL. But if any 35-year old is a safe bet, it is Tom Brady.