Jordan Spieth has sounded the alarm on the impact legalizing sports betting is having on golf—and what it could lead to next.

“I do think that betting in golf is something that’s going to have to be tackled here soon,” Spieth said Tuesday at his pre-tournament press conference ahead of this week’s PGA Tour event, the John Deere Classic in the Quad Cities. 

“In golf, it’s tricky because you could actually impact the outcome if you wanted to,” Jordan Spieth said. “It may not last very long, but you could impact a shot if you wanted to. I don’t know of another sport that you could impact as a fan like you can golf. So I don’t know how much that’s having to do with it, if it’s different than it used to be.”

Poor crowd behavior was the dominant storyline at last year’s Ryder Cup at Bethpage Black—also on Long Island—as the home U.S. fans turned ugly against the dominating European team. 

At the WM Phoenix Open in February, an influencer paid a fan $100 to yell during the backswing of Mackenzie Hughes. Both were ejected. Those types of events often go viral on social media, as cell phones are allowed at professional golf tournaments except for the Masters.

Jordan Spieth Press Conference

“I’ve also played rounds with guys who were not treated well 10, 15 years ago,” Jordan Spieth said. “I don’t think it’s a crazy new thing. … I will say that from what I’ve seen, a lot of times it has to do with betting, and that is in the last five years.”

The PGA Tour has official betting deals with DraftKings and FanDuel. The tour has yet to sign any formal pact with a prediction market.