Young was hitting .194 with seven home runs and 28 RBIs in 103 games when he was sent down Monday. He had two hits in his last 30 at-bats, and his average has not been above .205 since April 30.
The 25-year-old lost playing time in center field recently to rookie Gerardo Parra.
In 2007, Young became the first rookie in major league history to have 30 homers (32) and 25 stolen bases (27) in the same season as Arizona won the NL West.
Young hit .237 that season and .248 in 2008, when he led the team with 42 doubles and added 22 homers.
He signed a five-year $28 million contract extension in April 2008.