The Zags had a hard time deciphering Illinois' constant pressure to win their opener, while the Wildcats needed 30 minutes to find themselves in beating Iowa State.
Gonzaga (4-0) will play Arizona in the semifinals tonight, while IL (1-2) wakes up early to play in the brunch bracket against Iowa State.
Gonzaga coach Mark Few said he had a "nice little calmness" even as Duke tied the game late because he trusted his players.
Barrett's showmanship caught the attention of some big basketball names and had others wondering whether this Duke team could hang with the worst in the NBA. With huge experience with Frank Kaminsky and Sam Dekker, the Badgers knew what to do late in a close game and pulled out a win because of that.
Trent Frazier of IL drives for a first-half basket. They actually looked inconsistent through their first two games at the Maui Invitational, but they punched Duke in the mouth early on Wednesday and never looked back en route to a 16-point second-half lead. With this being the second night of a back-to-back for the Blue Devils and with the experience of this Tigers roster, this one could be a much tighter affair.
"I thought we looked young", Krzyzewski said after the loss. "I was letting those shots get to me, but the coaching staff and my teammates helped me get through that".
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Rui Hachimura scored 20 points and the Zags beat a No. 1 team for the first time while ending the Blue Devils' unbeaten streak on the Valley Isle (17-1).
The Blue Devils ran roughshod over one top-5 team to open the season, making then-No. Hachimura and Brandon Clarke then both recorded a pair of blocks in the final minute.
Marcquise Reed scored 24 points and grabbed nine rebounds as the Tigers cruised past the Bulldogs in the second round of the Cayman Islands Classic at George Town.
Robert Collias is at firstname.lastname@example.org.
With the Bulldogs up 47-33, Barrett drilled a 3-pointer with 1:05 to play.
Trent Frazier had 15 points to lead IL (1-3), which will face Xavier in the seventh-place game. Totals 27-70 14-19 78.
The 20-year-old junior shot 7-for-14 from the floor and 5-for-9 from the line for a team-high 20 points, and added seven rebounds, five assists and three blocks in the 89-87 win over a No. 1-ranked Duke team featuring several highly touted pro prospects, including likely top National Basketball Association pick Zion Williamson. Assists-Gonzaga 16 (Perkins 9), IL 10 (Dosunmu, Jordan 3).