EDEN PRAIRIE, Minn. -- They will forever be linked by a serendipitous twist, the worst injury of Tom Brady's career giving way to the best opportunity of Matt Cassel's. But six years after their time together in New England ended, the two quarterbacks still share a lot more than that.

Brady and Cassel remain good friends off the field. They play golf, see each other's families, work out together during the offseason in Southern California and still talk every other week during the season.

Matt Cassel said he learned a lot from Tom Brady from their days as teammates with the Patriots. AP Photo/Kathy Willens

Cassel hadn't started a game since high school before a hit from Kansas City Chiefs safety Bernard Pollard tore Brady's ACL during the 2008 season opener, and a solid season in Brady's absence made Cassel a rich man the next spring, when the Chiefs traded for him and gave him a six-year, $62 million contract.

But the two quarterbacks never faced each other during Cassel's time in Kansas City, and this Sunday, with the Patriots coming to Minnesota for the Vikings' home opener, Brady and Cassel will be competitors on the field for the first time.

"We probably won’t talk this week, I’m guessing," Cassel said. "At the same time, he’s a great friend. He was a great mentor to me when I was there. Like I said, I’m really grateful that I had that opportunity to work with him and learn from him."

When the Patriots spent a seventh-round pick on Cassel in 2005, he came to a team that had just won its third Super Bowl in five years.

"He was very talkative as a rookie," Brady said. "I had to make sure he didn't overstep his bounds from time to time. But that's part of his personality -- he's very energetic, he's very intense. He's always been that way, since the day I met him."

Brady's advice, Cassel said, taught him how he needed to handle himself in the NFL.

"I remember when I was a young quarterback and we’re out at practice and I forgot a motion, and I still hit the pass, but he got after me pretty good about forgetting the motion," Cassel said. "The whole point to why he did it, he said, ‘Look, you can’t be a guy and seen as a leader if you’re making mistakes, simple mistakes, on the field. You can’t be a guy that goes up and tries to get after somebody else if you’re making those mistakes.’ And I thought it was a great point and I’ve carried that with me wherever I’ve gone.

"I think I give all the credit to that, the fact that I was, as a young player, able to come in and learn from one of the best, if not the best over his career. Really, each and every day, watch the process that he went through, how he broke down defense, ask questions. And then for him to be so good to me to actually answer those questions and not blow me off like, ‘Hey, get out of here,' it was huge for my development as a player.”

Cassel has said what Brady did for him influenced how he works with Vikings rookie Teddy Bridgewater, and Cassel said Wednesday that he still follows the Patriots closely. Even though the friendship might be put on hold this week, the respect between Cassel and Brady hasn't gone anywhere.

"He's had to fight his whole career," Brady said about Cassel. "Things were never easy for him: they weren't easy in high school, they weren't easy in college, and certainly, when he got to the professional level, they weren't easy. He's had a lot of adversity, and he's dealt with it. I think that's made him a strong person, a strong player and really a great teammate. That's why he's the starting quarterback of a very good NFL team right now. I'm proud of him."