At $4.3 million, Patrick Mahomes' own rookie card was too rich

Mahomes' adorable baby girl welcomes him back to the Madden 99 Club (1:12)

Patrick Mahomes gets welcomed back into the Madden 99 Club for the third straight year by his fiancee and baby girl. (1:12)

ST. JOSEPH, Mo. -- Patrick Mahomes wasn't planning on buying his 2017 rookie card anyway, but as things turned out the bidding went well beyond what he would have paid.

"I don't know if I would have gone all the way up there," Mahomes said Friday from Kansas City Chiefs training camp about the recent sale of his signed rookie card for $4.3 million, a record for a football card. "I don't know the ins and outs of it like those dudes do. They've definitely used it as an investment and I'm sure they'll sell it later for more money.

"That's a lot of money. I'll say that. I knew it was going up for auction. I found out, but for it to go for that much, it shows that that business has been growing forever. I remember collecting cards as a little kid with my dad and to see how it's really blown up these days ... it really is a cool thing to see especially when it has your name on it.

Mahomes, shortly before the start of training camp, did purchase a piece of Sporting Kansas City, the city's MLS team. Mahomes last year bought into the ownership group of the Kansas City Royals and his fiancee, Brittany Matthews, is a co-owner of Kansas City's franchise in the National Women's Soccer League.

"It started a couple of years back," Mahomes said of his interest in Sporting Kansas City. "The people over there at Sporting, I love the way that they run their business and how they've really invested in that team.

"My love of soccer started with Brittany. I really wanted to be a part of it and she has a NWSL team. That's her thing and I wanted to do my own thing in a sense. And then always supporting the Kansas City community.

"The community has embraced me from Day 1. When I was behind Alex [Smith] and they were supporting Alex they still showed me love. When I came into the starting role they always believed in me. I want to show that same love to the community that they've showed me this entire time I've been here."

Mahomes in soccer will be a rival of Chiefs' chairman Clark Hunt. His Hunt Sports Group owns and operates FC Dallas of the MLS.

"I'm sure there will be a little rivalry there," Mahomes said. "We'll have a friendly little rivalry in that sense."