Quarterback Tom Brady signed a four-year extension with the New England Patriots that will make him the NFL's highest-paid player, a source close to the negotiations confirmed Thursday night.

Brady's contract is worth $72 million and guarantees him $48.5 million, a source familiar with the deal told ESPN NFL Insider Adam Schefter. The extension, which will be filed with the league Friday, will be added onto the final year of Brady's contract and runs through 2014, when he will be 37. Brady, 33, has said he wants to play until he's 40.

Brady, who was picked by the Patriots in the sixth round of the 2000 draft, is making $6.5 million this season in the final year of an earlier four-year, $48 million extension. The new deal will make him the league's top-paid player in terms of average annual salary.

"We've gone about our business in a diligent manner with very complicated, difficult labor environment," team owner Robert Kraft told the Boston Herald on Friday. "We've been able to secure Brady, Vince Wilfork, [Stephen] Gostkowski, [Leigh] Bodden, Tully Banta-Cain, people who have come here, worked hard and want to be here long term. We've done everything we can do.

"While our job is never done. I sort of like this team over the next few years. We have a great coach, and one of the finest quarterbacks to have ever played the game for another five seasons."

Sports Illustrated's Peter King broke news of the agreement during halftime of NBC's broadcast of the NFL's season-opening game between the New Orleans Saints and Minnesota Vikings, saying he spoke to Kraft, who told him the deal was finished.

The agreement comes on the same day Brady was involved in a two-car accident near his home in Boston. He walked away from the crash uninjured and practiced with the Patriots in the afternoon.

Tom Brady practiced despite being in a car accident earlier Thursday. Later, he finalized a four-year contract extension. AP Photo/Stephan Savoia

It's unlikely the accident had any impact on the deal's completion Thursday, but Brady wanted to get the contract finished before Sunday's season opener against the Cincinnati Bengals. After all, it was two years ago when Brady's season was ended in the first quarter of the first game when Kansas City Chiefs safety Bernard Pollard rolled into Brady's knee, tearing his ACL.

"You count your blessings when you come off the field," Brady said Wednesday. "I think you have a new appreciation when you do come off the field, win or lose. You're trying to win every time out, obviously. But I think you also pinch yourself every time you walk off the field healthy and say, 'Man, at least I get a chance to go out next week and play also.' "

Brady's extension has been the hottest topic of the summer in New England, although Brady downplayed its importance even as reports surfaced that his relationship with the team had become strained.

"I really love being here and playing for Mr. [Robert] Kraft and Jonathan [Kraft]," Brady said Wednesday. "Our relationship isn't based on how much money he pays me. 'I'm great when he pays me what I want, and I hate him when ... .' I mean, that's not the way relationships work.

"I've had friends like that in the past. That's not the type of friends you want. It's very unconditional -- the relationship I have with coach [Bill] Belichick and the whole organization. I'm blessed to play here and I love playing here. I think we're all fortunate to play for a team that's committed to winning. If that's the goal for all of us, if you want to win, you really appreciate where you're at."

On Wednesday, when reports indicated an extension was close, Brady sidestepped contract questions, saying his focus was on preparing for Sunday's season opener.