Oregon dropped eight spots to No. 21 in the Associated Press Top 25 after splitting two games at the 2K Empire Classic in New York.
Oregon arrived at Madison Square Garden ranked No. 13 before losing 77-69 against unranked Iowa. The Hawkeyes moved into the poll at No. 20 this week after winning the two-day tournament.
The Ducks followed up with an 80-65 win over 15th-ranked Syracuse, which dropped out of the poll after losing two games at the tournament.
The Ducks (3-1) return to Matthew Knight Arena to face Green Bay (3-2) Tuesday night at 7 p.m.
UCLA moved up from No. 20 to No. 17 to pass Oregon as the highest-ranked Pac-12 school.