BERKELEY – While the Cal volleyball team was euphoric over the debut of Savannah Rennie on Friday night, the Bears still left Haas Pavilion feeling troubled. They struggled mightily in a three-set loss to Utah, and spirits were as low as they have been all season during their post-match team meeting.

The solution? Focus on themselves.

The Bears stunned No. 19 Colorado on Sunday, 25-22, 25-23, 18-25, 25-21 for their first Pac-12 victory of the season. Sophomore middle blocker Belen Castillo had a career-high 16 kills and matched her career-best with six blocks. Junior Christine Alftin tied a career-high with 16 digs to go along with 13 kills. And Cal registered 14 blocks as a team – its highest total since Oct. 31, 2014 against Oregon.

"There were such mixed emotions Friday, between the high of Savannah and the low of playing maybe our worst match of the season," Cal coach Rich Feller said. "Our locker room talk after or match on Friday was very low. We were happy Savannah was back on the court, but we were very disappointed. They were hard on themselves and the coaches were hard on the players."

Rennie made her college debut Friday after undergoing a liver transplant in May, and while everyone associated with the Cal program experience an emotional high, her appearance on the court was associated with the Bears' fifth straight loss.

Feller said the Bears finally started worrying about themselves more than the opponent scouting report Sunday – a mindset the coaching staff has been trying to implore to the team all season.

"That was a great maturing aspect of our team today," Feller said. "We showed we can beat a good team."

Castillo was a huge reason why. Playing their third straight match with leading attacker and blocker Jenelle Jordan, Castillo more than filled the void of Jordan's production. She played her most aggressive match of the season, swinging with authority and dominating the net.

"I feel like we always have that fire in practice but we don't always come out with it in games," Castillo said. "We are all so competitive and we wanted it so bad today. You could see it in everyone's faces. We were determined. There was never a second I didn't think we were going to win that match."

Castillo moved from the right side to the middle this season and registered double-digits in kills for the third time this season on Sunday. She bettered her previous career-high of 15 kills set last season at Kansas State, and equaled the six blocks she had earlier this season against Northeastern.

Castillo closed out the match with four kills in a row.

"We've tried to get Belen to get more aggressive," Feller said. "Tonight was a huge step toward that. She doesn't have to change her personality off the court, but on the court we needed more of a presence from her. She had that tonight."

Junior Caihla Petiprin and freshman Maddie Haynes each also set career-highs with six blocks, while redshirt sophomore Ashten Smith-Gooden pitched in with 11 kills.

The Bears made big plays at the end of each of the first two sets to take command. Cal trailed the first set 22-21 but scored four in a row to close it out. Haynes came up with a thunderous solo block to end it. The second set was tied 23-23 but a kill by Alftin and a hitting error on the Buffs ended it.

"I don't think anybody is satisfied," Feller said. "We all know how hard we work, and they all know now there is a bigger light at the end of the tunnel. They can look at who Colorado is beaten, and it shows we can compete with anybody."

The Bears return to the Haas Pavilion court Friday against Arizona State at 6 p.m. The match will be televised by the Pac-12 Networks.