If you were shocked by the length of Patrick Mahomes' new 10-year, $503 million contract with the Kansas City Chiefs, don't worry, you're not the only one. So was Patrick Mahomes. When Mahomes got word from his agent, Leigh Steinberg, that he would be getting a 10-year extension from the Chiefs, the quarterback didn't know what to think, and that's because he didn't even know it was legal for NFL teams to give out 10-year deals. 

Mahomes revealed that fact this week when he was asked about his record-setting contract during a one-on-one interview with

"There were two things I said when we went into negotiations: I wanted to keep great players around me and I wanted to have long-term security for my family," Mahomes said. "I certainly wasn't thinking 10 years. I didn't even know NFL contracts did that."

Donovan McNabb didn't know that NFL games could end in ties, and Patrick Mahomes didn't know a 10-year deal was possible.

In Mahomes' defense, he probably wasn't aware that lengthy deals were possible because they almost never happen. As a matter of fact, before the Mahomes deal got done, there had only been five extensions of 10 years or more in NFL history. The Chiefs quarterback was just 9 years old when the last 10-year deal happened in 2004, which involved Michael Vick. 

Apparently, NFL teams became slightly enamored with the idea of a 10-year deal at the start of the century, because all five 10-year extensions that came before the Mahomes deal happened in a three-year period between March 2001 and December 2004. The first 10-year extension was given to Brett Favre, which was then followed by Drew Bledsoe (March 2001), Donovan McNabb (September 2002), Daunte Culpepper (May 2003) and Vick (December 2004) all getting long extensions. 

One thing all of those deals have in common is that none of them panned out. Not a single player on that list ended up playing out the full 10 years of his deal, which might be one reason why NFL teams started to shy away from the lengthy contracts. 

As for Mahomes, besides the length of the deal the quarterback's contract also includes several other interesting clauses. For instance, there's a list of sports that he's no longer allowed to play, and you can read about those by clicking here

For more on the Mahomes deal, make sure to click here to check out his interview with where he gives the inside scoop on his record-setting contract plus how he feels about the expectations that come along with signing the largest deal in sports history