CHATTANOOGA, Tenn. -- Chattanooga coach Wes Moore's wife gave him one piece of advice before heading out of town to celebrate her grandmother's 100th birthday.

"The last thing she told me before she left was, 'Try not to embarrass the family,'" Moore quipped after his team stunned No. 20 Tennessee 80-71 Friday in the Lady Vols' first game of the post-Pat Summitt era.

Instead, the team that had been embarrassed by Tennessee each of the last two seasons -- losing 103-43 in 2010-11 and 90-47 last year -- turned the tables on one of the signature programs in women's college basketball.

Tennessee's first game without Summitt revealed just how much has changed for Tennessee. Taylor Hall scored 24 points as Chattanooga shocked the Lady Vols to spoil the head coaching debut of Holly Warlick, who spent the last 27 seasons as an assistant on Summitt's staff.

"I think we were a little anxious, sure," Warlick said. "We're young. A new coach. We're playing in a hostile environment. But what it comes down to is you've got to take care of business. We didn't."

Chattanooga never trailed in the second half and beat Tennessee for the first time since Jan. 26, 1973. The Lady Mocs had lost the last 19 games in this series.

By the end of the game, a McKenzie Arena crowd of 8,468 that had seemed equally divided at the start of the night was gleefully chanting "UTC!" Several dozen students stormed the court afterward to celebrate with the Lady Mocs.

Meighan Simmons scored 21 of her 23 total points in the second half for Tennessee, which committed 26 turnovers and had only six assists.

"We have to play Tennessee basketball," Simmons said. "That's something we didn't do tonight."

Summitt, who announced last year she had early-onset dementia, stepped down in April after collecting 1,098 wins, eight national titles and 18 Final Four appearances in 38 seasons. She was succeeded by Warlick, a former three-time All-America guard for Tennessee who was the first athlete at the school to have her number retired.

Summitt remains on staff as head coach emeritus and attends most of Tennessee's practices. She watched Friday's game from the fifth row in a narrow section behind and to the right of Tennessee's bench. Summitt was approached for dozens of photographs and autographs by fans of both teams before the opening tip.

Warlick stood in front of the bench throughout the night with her arms folded or her hands on her hips.

"As long as we learn from this, it's OK," Warlick said. "If we keep making the same mistakes, we're not going to get any better."

The head coaching switch isn't the only change surrounding Tennessee this season. The Lady Vols don't return a single player who started an NCAA tournament game during their run to a regional final last season. Tennessee's roster includes four freshmen, four sophomores and only one junior and two seniors. Tennessee's No. 20 preseason ranking is its lowest position in the Top 25 since February 1985.

All those Tennessee underclassmen had plenty of nerves Friday. Tennessee needed Ariel Massengale to sink a 25-footer at the buzzer just to force a 28-28 halftime tie with Chattanooga, a team that lost 90-47 to the Lady Vols last season.

"I thought in the first half they got kind of frustrated," Chattanooga guard Kayla Christopher said. "They didn't know what to do. They had never been in that situation before."

Chattanooga pulled ahead by making six of its first seven shots -- including a trio of 3-pointers -- in the second half. Chattanooga built on that lead by outhustling the Lady Vols.

In one sequence, Hall got a putback and drew a foul to give Chattanooga a 45-39 lead. Hall missed the ensuing free throw, but 5-foot-9 guard Kayla Christopher got the rebound and made a 3-pointer to extend the Lady Mocs' advantage to 48-39.

Hall was the best player on the floor all night long. At one point in the first half, Hall was 4-of-4 from the floor while her teammates were a combined 1-of-15.

"So many times we've played Tennessee and dug a hole in the first half," Moore said. "Taylor hit some big shots to keep us in the game."

Once Hall started getting more help from her teammates, Chattanooga took the lead and never looked back.

After shooting 36.7 percent (11-of-30) in the first half, the Lady Mocs shot 56.3 percent (18-of-32) and scored 52 points in the second half. Chattanooga finished the game with 17 assists and only 13 turnovers.

"Until defense becomes a priority for us, we're going to struggle," Warlick said. "Right now, our defense is not a priority. I hope this is a great lesson for them."

This wasn't the first time the Lady Vols struggled to leave Chattanooga with a victory. When the Lady Vols last played Chattanooga at McKenzie Arena four years ago, they also had a freshman-laden team and trailed late in the second half before squeaking out a 66-63 victory.

This time, Chattanooga closed the deal.

"This is special," said Moore, a 1986 Tennessee graduate. "It will be something we never forget. That's what I told them in the locker room. You've done something you'll never forget."