Powell pushed the Bruins to a 69-56 victory in Boulder. He made eight of 13 shots and scored 19 points. The rest of the Bruins shot 34% from the field.
The Bruins and Buffaloes play again Thursday in Pauley Pavilion.
"Norman Powell is a phenomenal athlete," Boyle said. "He gets a head of steam going, he is hard to deal with."
Powell showed that again against USC on Saturday. He had a career-high 21 points, again making eight of 13 shots. That included two three-pointers.
"He has improved his outside game," Boyle said. "It has never been his strength, but he was capable. He is becoming a much more complete player."
Powell, who averages 11.4 points per game, has struggled from the outside this season. He is shooting 21% on three pointers.
But Boyle saw him make two in Boulder. They came on back-to-back possessions to break a 20-20 tie. Powell had 13 first-half points, helping the Bruins build a 36-29 halftime lead.
"His athleticism, and now that added skill, makes him someone you have to wary of," Boyle said.