<p><b>UPDATE: </b>ESPN is now reporting that Mahomes' new 10-year contract extension is worth up to $503 million, making it the largest contract in pro sports history.</p><p><b>UPDATE: </b>The Kansas City Chiefs have officially announced the signing of quarterback Patrick Mahomes to a 10-year contract extension. From <a href="https://www.facebook.com/KansasCityChiefs/">The Kansas City Chiefs</a> Facebook page:&nbsp;</p><div><iframe src="https://www.facebook.com/plugins/post.php?href=https%3A%2F%2Fwww.facebook.com%2FKansasCityChiefs%2Fposts%2F10158526601933373&width=500" width="500" height="448" style="border:none;overflow:hidden" scrolling="no" frameborder="0" allowTransparency="true" allow="encrypted-media"></iframe></div><p>KANSAS CITY, Mo. -- Patrick Mahomes and the Kansas City Chiefs have reached a deal on a 1-year contract extension, ESPN's Adam Schefter is reporting today.</p><p>Schefter reported that league sources have told him the contract extension is worth $450 million, and barring accident or trade, will keep the star quarterback with the team through the 2031 season. The contract also includes a $140 million injury guarantee, a source told Schefter. </p>

UPDATE: Chiefs make it official, sign Mahomes to 10-year extension