Tad Boyle didn't notice a "light bulb" moment for Xavier Johnson.

The talented 6-6 freshman forward from Los Angeles says his game hasn't changed.

But Andre Roberson believes Johnson had an awakening after Colorado's disappointing 78-75 loss to UCLA on Jan. 12.

"I definitely would say after the UCLA game, (Johnson) came and hooked it up in practice and got after it," Roberson said. "He definitely picked it up there, and I've seen a lot more progress, especially getting the offense a lot more and moving without the ball."

Since CU's only home defeat of the season, Johnson has averaged 11.3 points, 3.7 rebounds and led the Buffs in highlight dunks.

During Thursday's 75-54 victory over Stanford, Johnson had four poster-worthy slams and a 3-pointer in 24 electrifying minutes.

"I just think it's the fact that I'm getting more used to it," Johnson said of playing at a Pac-12 level. "The more experience you have playing collegiate basketball, the better you get. That's where I'm at right now."

Boyle said it took some time for Johnson, a star at powerhouse Mater Dei (Santa Ana, Calif.) High School with fellow CU freshman Eli Stalzer, to adjust to some of the mental challenges college athletes face.

"I think he has really matured in a sense," Boyle said. "You get that when you get really physically talented freshmen. Because he has been able to get by with his athleticism and his strength. In high school he could bully anyone he wanted to bully on a basketball court. Now he has to think a little bit and he has made some great strides."

The Buffs (13-6, 3-4) have made some significant strides on the defensive end since the UCLA game and are seeking their third consecutive victory on Sunday against Cal at the Coors Events Center (1:30 p.m., Root Sports).

Boyle is hoping his team will play with the same energy and intensity it showed while out-rebounding the Cardinal 48-30 and holding the visitors to 31.3 percent from the field.

"That's the challenge. We've talked about trying to put a 40-minute game together, that's hard enough. Now once you've done that you've got to put a season together," Boyle said. "Maybe I'm getting greedy there. That's got to be the challenge: We play with that edge, that emotion, that passion every night.

"Sometimes you're going to play with it and the other team is going to play with it. That's when you get into college basketball games that are pretty darn fun to watch."

Roberson was spectacular against Stanford, matching his career high with 20 rebounds. The Pac-12's reigning rebounding champion currently leads the nation (11.9 rpg) in that category.

"I was just getting tired of the fact that the coaches were getting on us about last year and how Stanford just bullied us and outplayed us and beat us on the boards," Roberson said. "I just took the initiative to get after them."

The Bears (11-7, 3-3) feature the conference's leading scorer, 6-6 junior guard Allen Crabbe (19.9 ppg), who will be defended by both Spencer Dinwiddie (6-6) and Roberson. Crabbe and backcourt mate Justin Cobbs are the highest scoring 1-2 punch in the Pac-12, combing for an average of 34.2 points.

Cal began the road trip with a 62-57 win at Utah. Crabbe made four 3-pointers and finished with 23 points.

"I think we really, really have been doing some soul-searching and we were ready to get back on track," Bears guard Brandon Smith, who returned after a six-game absence from a concussion, told the Oakland Tribune. "I'm hoping that is the brand of basketball we continue to play through the rest of conference because we're capable of bringing that every night."

The CU-Cal series is tied 10-10. The Buffs lost in Berkeley last season before beating the Bears in Boulder and in the semifinals of the Pac-12 Tournament.

Cal's other two conference wins this season were against USC and Washington State with losses to UCLA, Washington and Stanford.

CU returned to the form it showed in winning the Charleston Classic and also beating Colorado State early on the season with all five starters scoring in double figures against Stanford.

"I feel like we're unstoppable when everybody gets on the same page and is clicking," Roberson said. "Playing as a team, that's what coach Boyle has been wanting since the beginning. We showed a little bit of that in Charleston, we had a little slump, and we're picking it back up now."

Follow Ryan on Twitter: @RyanThorburn

CU men's hoops preview

SUNDAY: The Colorado Buffaloes (13-6, 3-4) host the Cal Bears (11-7, 3-3) at 1:30 p.m. at the Coors Events Center.

BROADCAST: Television on Root Sports with Steve Physioc (play-by-play) and Corey Williams (analyst). Radio on KOA (850 AM) with Mark Johnson (play-by-play) and Chad Brown (color). Follow on Twitter: @RyanThorburn.

CU STORY LINES: The Buffs are coming off an impressive 75-54 victory over Stanford on Thursday in front of the fourth-largest crowd (11,212) in Coors Events Center history. ... Andre Roberson matched his career high with 20 rebounds as CU out-rebounded the Cardinal 48-30. The 6-7 junior forward leads the nation in rebounding (11.9 rpg). ... All five starters scored in double figures against Stanford, led by Askia Booker's 13 points on 6-for-9 shooting. ... Freshman wing Xavier Johnson has scored 25 points on 10-for-15 shooting during the Buffs' two-game win streak. ... CU has only made 17 3-pointers over the last six games.

CAL STORY LINES: The Bears are coming off a 62-57 road win at Utah on Thursday. ... Allen Crabbe, the Pac-12's leading scorer at 19.9 points per game, sparked Cal's offense with 23 points, including four 3-pointers. Spencer Dinwiddie and Roberson will try to slow down the dynamic shooting guard. ... Crabbe and Justin Cobbs are the highest scoring 1-2 punch in the Pac-12, combing for an average of 34.2 points. ... Mike Montgomery, who was 393-167 during 18 seasons as the head coach at Stanford, is seeking his 100th win at Cal Sunday.

KEY STAT: CU, which is 40-5 at the Coors Events Center under Tad Boyle, drew a sellout crowd of 11,212 for Stanford. CU is second in the Pac-12 in attendance (10,307) behind Arizona (13,920) this season.

COACHES: Boyle is 61-31 in his third season at CU. Mike Montgomery is 99-54 in his fifth season at Cal.

PROBABLE STARTERS: Colorado -- F Andre Roberson, 6-7, Jr., 10.6 ppg, 11.9 rpg; F Josh Scott, 6-10, Fr., 12.9 ppg, 5.7 rpg; G Spencer Dinwiddie, 6-6, So., 14.4 ppg, 2.6 apg; G Askia Booker, 6-1, So., 14.1 ppg, 2.5 apg; G Sabatino Chen, 6-4, Sr., 4.6 ppg, 2.4 rpg. Cal -- F Richard Solomon, 6-10, Jr., 8.1 ppg, 6.4 rpg; F David Kravish, 6-9, So., 7.8 ppg, 7.4 rpg; G Allen Crabbe, 6-6, Jr., 19.9 ppg, 5.5 rpg; G Justin Cobbs, 6-3, Jr., 14.3 ppg, 4.1 apg; G Tyrone Wallace, 6-4, Fr., 6.8 ppg, 4.9 rpg.

SERIES: Tied 10-10. The Buffs defeated Cal 70-59 in the Pac-12 Tournament semifinals last season and have won seven of the eight meetings in Boulder.

UP NEXT: The Buffs play Utah next Saturday at the Huntsman Center (12:30 p.m., Root Sports).