As Justin Upton pulled on his brand-new Arizona Diamondbacks jersey, he tried to recall what he was doing at this time last year. "A year ago, we just started tryouts for my high school team," Upton said this week. Tryouts? Upton chuckled when asked if he had to try out for the varsity at Great Bridge High School in Chesapeake, Va. "No, not really," he said. In June, the Arizona Diamondbacks picked him first overall in the amateur draft. After several months of negotiations, the club gave Upton a $6.1 million signing bonus -- the largest in a minor league contract for a drafted player who was not a free agent. And now the 18-year-old is at the Diamondbacks' training camp as a non-roster invitee. Upton showed up nearly a week before the reporting date for position players. The 6-foot-3, 205-pounder started hitting balls over the fence in his first swings against big league pitching. "Unbelievable impression," manager Bob Melvin said after watching Upton in the batting cage. "He's got great actions for an 18-year-old kid. A wooden bat looks natural in his hands. He resists going out there and trying to hit home runs on every ball in batting practice. He hits the ball the other way. Just a very impressive 18-year-old."