Play more freely, don't worry if you miss a shot, play with confidence, he told the talented freshman.
Trier took it to heart and the Wildcats are seeing the dividends.
Trier scored 27 points, including six in the final 70 seconds to help No. 13 Arizona pull away late and beat Fresno State 85-72 on Wednesday.
''Tonight, he was the difference between us winning and losing,'' Miller said.
Arizona (8-1) had a hard time shaking Fresno State, allowing the Bulldogs to hang around until the closing minutes.
The Wildcats pulled it out behind Gabe York and Trier.
York was more of a distributor in the first half, but made the big shots when Arizona needed them. The senior hit a pair of 3-pointers - one banked in - and scored on drive the basket, getting nine of his 12 points in the final 2:51.
Trier was good all night, going 3 for 5 from 3-point range and making 8 of 11 shots overall.
Ryan Anderson added 17 points to help Arizona extend the nation's longest home winning streak to 43 games.
''Anytime somebody tells you you can go out there and be yourself and do what you do best, it makes you feel confident and establish your comfort level,'' said Trier, who has 41 points on 20 shots the past two games.
Harris had 23 points and Watson added 14, but the Bulldogs came up just short for the second straight time against a Top 25 opponent.
Fresno State, which lost to Oregon by five on Nov. 30, made 12 of 33 shots in the second half and missed all five of its 3-point tries after making all five from behind the arc in the first half.
''In the first half, we still got where we were trying to go in terms of attacking the paint and playing in the paint,'' Fresno State coach Rodney Terry said. ''In the second half, I thought they did a much better job of making it difficult for us to play in the paint and have those opportunities.''
The Wildcats had their biggest win of the season on Saturday, rallying from a shaky first half with a super second to knock off then-No. 13 Gonzaga in Spokane.
The same script played out against Fresno State.
Arizona was solid offensively in the first half, hitting 18 of 35 shots. The Wildcats struggled on the defensive end, allowing the Bulldogs to get to the rim and leaving open shots from the perimeter.
Fresno State made 19 of 33 shots in the first half to lead 46-43.
Harris, who scored a season-low 12 points against Cal Poly, had 17 by halftime, hitting 7 of 12 shots and all three of his 3-point attempts.
When the Bulldogs came out of the locker room, they were greeted with a lot more intensity - from the Wildcats and their fans. But after withstanding Arizona's initial push, Fresno State shoved back, continuing to hit shots.
Arizona stretched the lead to nine with a short burst, yet the Bulldogs kept hanging around, pulling within one at 71-70.
But York hit a 3-pointer in transition and banked in another to put Arizona up 77-70 with 2 minutes left. Trier closed it out with four free throws and an uncontested dunk.
''It's still early in terms of evolving into a really good team, but I think they're going to have a really good team,'' Terry said of Arizona.
Arizona point guard Kadeem Allen appeared to suffer a serious injury went he went down on a non-contact play. The junior lay on the floor for about a minute and had to be helped off the court, unable to put any weight on his right leg.
Miller said Allen sprained his right ankle, but wouldn't know how long he will be out for a few days. Allen finished with 13 points and five assists.
Fresno State: The Bulldogs have lost eight straight to Pac-12 teams. ... Fresno State scored 23 points off Arizona's 13 turnovers.
Arizona: Junior G Elliott Pitts did not play due to a personal issue. ... The Wildcats have won 29 straight non-conference home games.
Fresno State hosts Pacific on Saturday.
Arizona hosts Missouri on Sunday.