Patrick Mahomes signs richest NFL deal ever

Kansas City Chiefs quarterback Patrick Mahomes signed a 10-year contract extension on Monday worth up to $503 million, ESPN reports.

Why it matters: It's the largest contract in the history of American sports and almost double the career earnings of Eli Manning, the highest-paid player by salary in NFL history.

• "We're staying together ... for a long time. We're chasing a dynasty," Mahomes said in a video posted on Twitter.

The big picture: Mahomes' 12-year deal — a 10-year extension, plus two years on his current contract — is incredibly rare. The Dallas Cowboys' Tyron Smith is the only other NFL player with a contract lasting more than six years.

Zoom out ... Highest average annual contract value by sport, per ESPN:

• NBA: Damian Lillard ($49m)
• NFL: Mahomes ($45m)
• MLB: Gerrit Cole ($36m)
• NHL: Connor McDavid ($12.5m)