Sixteen-year-old Kyle Giersdorf threw the ball to right fielder turned ceremonial catcher Bryce Harper.
Umpire Phillie Phanatic called it a strike.
Giersdorf won $3 million as the first Fortnite World Cup solo champion. He's getting used to being a celebrity gamer.
"It's been kind of crazy. I'm not real used to it. It's overwhelming really. The hardest thing getting used to is all these people noticing me. Like before I was just kind of no one, so now it's a little bit different," Giersdorf said.
The teen has also learned the downside of fame.
Giersdorf was livestreaming on Saturday when he was "swatted," a prank that aims to prompt police and SWAT teams to respond to fake emergencies.
Upper Pottsgrove Police Cpl. Albert Werner told USA Today a caller told police "he was Kyle and said he had shot his father multiple times." Police called the home before entering and the teen's father said everything was fine
The situation at his home was resolved peacefully.
The Associated Press contributed to this report.