Justin Upton, the 18-year-old shortstop who was the top pick in the 2005 major league amateur draft, agreed to a minor league contract with the Arizona Diamondbacks that includes a $6.1 million signing bonus payable over five years. Arizona announced the agreement Friday and said Upton will be introduced at a news conference Monday. The signing bonus is the largest in a minor league contract for a drafted player who was not a free agent, topping the $5.3 million outfielder Joe Borchard got when he signed with the Chicago White Sox in July 2000. "This is a significant step for our organization and we look forward to seeing this talented young man in uniform," general manager Josh Byrnes said. Upton follows another top young shortstop, Stephen Drew, who is expected to play for Triple-A Tucson in his second season in the Arizona organization. Upton hit .519 during his senior season at Great Bridge High School in Chesapeake, Va., with 11 home runs and 32 RBI in 54 plate appearances. He scored 29 runs and stole seven bases. Upton, 6-foot-3 and 205 pounds, was selected Gatorade High School Player of the Year and was a consensus high school all-American. He gets $400,000 of the signing bonus upon approval of the contract, $400,000 at the end of the year, $1 million each in 2007 and 2008, $1.3 million in 2009 and $2 million in 2010.