Without Metu, host USC outlasted UNC Asheville 103-98 in double-overtime on Tuesday night to advance to the second round.
"Chimezie Metu has made a personal decision not to participate in the NIT as a precautionary measure to eliminate the risk of injury leading up to the NBA draft," Enfield said in a statement.
The decision did not come as a surprise as Enfield allowed for the possibility Metu would not play on Monday, a day after the Trojans were a controversial omission from the NCAA tournament field.
Metu was the Trojans' leading scorer and rebounder this season, averaging 15.7 points and 7.4 rebounds per game. He is ESPN.com's No. 34-ranked draft-eligible NBA prospect and generally viewed as a likely late first-, early second-round pick.