No. 21 Arizona (2-0) was good at both ends, shooting 56% while nabbing 14 steals. The Wildcats turned a tight game at halftime into a rout with a 17-2 second-half run behind the freshman trio of Mannion, Green and Zeke Naji. Nnaji finished with 19 points, Mannion had nine assists and Green was 4 for 7 from 3-point range.
Illinois (2-1) was able to hang with the Wildcats in the first half of a high-level game with more than two dozen NBA scouts on hand.
The Illini went cold in the second half and struggled holding onto the ball, turning it over 22 times. Ayo Dosunmu led Illinois with 15 points and Trent Frazier added 14.
Sunday night's game was the first big test for both teams. Arizona used its size advantage to open the season with a blowout victory over Northern Arizona.
Illinois needed overtime to beat Nicholls State at home and blew out undersized Grand Canyon in a rowdy atmosphere Friday. The GCU part got the Illini ready for another of college basketball's best atmospheres at McKale Center.
Illinois made seven of its first eight shots and Frazier had eight points in the first 4 1/2 minutes. Mannion matched him, scoring on a 3, a floater, a putback and set up Nnadi for a dunk with a baseball pass in traffic .
The offensive show continued the rest of the half. Frazier had 12 points and Illinois hit 15 of 27 shots. Mannion had 11 points, Arizona went 16 for and led 39-38 on Max Hazard's last-second 3-pointer .
Arizona tightened up on defense to start the second half and went on an early 8-0 run to go up nine.
Illinois answered with a 7-0 run, but Arizona scored 15 straight points behind Green and Mannion to go up 68-52. Illinois went 5:11 without a field goal and shot 10 of 26 in the second half.
Illinois was long and athletic enough to hold its own against a Top-25 team like Arizona, but must cut down on the turnovers and get a better offensive flow.
Arizona's talented freshman can take the Wildcats a long way if they keep playing like this.
Illinois hosts Hawaii on Nov. 18.