Teammates at Great Bridge High School, Chesapeake, Va., "mean more to me than the draft right now," Upton told USA Today. "I need to help myself and my team win a state championship."
Upton and his Wildcat teammates headed for regional semifinal playoffs Wednesday.
The 17-year-old named Gatorade's high school player of 2005 and watched by up to 20 scouts at a time also looked forward to next Tuesday's draft.
Should he be the No. 1 choice, Upton and his older brother B.J., the No. 3 MLB draft in 2002, would be the highest-drafted brothers in MLB history.
Despite a competitive brother who often made him cry, Upton said he and his 20-year-old sibling are close.
"I wouldn't be the player I am today if (B.J.) cut me any slack," Justin said.