Christmas scored a season-high 35 points, including three straight 3-pointers during a game-changing stretch that helped Temple upset No. 8 Tennessee 88-72 on Saturday.
Owls fans stormed the court in a wild celebration for coach Fran Dunphy's biggest win in three seasons.
"We played about as good as we could play," Dunphy said.
"Everything just came together."
Christmas delivered with a sensational second half when he hit six of his seven 3-pointers for the Owls (5-3). He made 10 baskets in the second half, holding back the nipping Volunteers and turning this into a rout.
"I didn't think I'd get the looks I got today," Christmas said. "I usually don't get that many good looks. Fortunately, I was knocking them down."
Tennessee (6-2) never led in the game, but cut the deficit to four midway through the second half. Christmas then hit three 3s that stretched the lead to 15 points.
Sergio Olmos had five blocks and a career-high 19 points, including two baskets during Temple's 8-0 run to start the game, while Ryan Brooks had 16 points and 10 rebounds.
"It was a huge game. I was just feeling great," Olmos said.
"I was feeling like I could jump more than I ever could."
Tyler Smith led the Volunteers with 17 points and Bobby Maze had 15.
The Volunteers were just the sixth top 10 team to play at the Liacouras Center since 1997 and left to chants of "Overrated!"
from the raucous crowd. Tennessee's other loss came to then-No. 9 Gonzaga in November.
"There was something special going on," Dunphy said. "You felt like we were prepared."
The Owls raised a banner before the game celebrating their A-10 tournament championship, then went out and scored the first eight points. Tennessee coach Bruce Pearl called a quick timeout to calm his team and they would tie the score at 15 before falling behind for good.
"Our reputation is we're a team that plays hard and today I don't think we played that hard," Pearl said.
Christmas, a 6-foot-5 guard with a knack for explosive games, kept the upset hopes alive with a 3 to start the second half. He also scored the next six points to stick Temple's lead at 14.
Christmas went 7-for-14 from 3-point range and 12-of-22 from the field.
Then came the big run. The 38 percent 3-point shooter buried 3 in a row during a 17-6 run that also saw him hit a free throw when Pearl was whistled for a technical. The normally staid arena was almost filled to the rafters and got about as loud as its ever been when Christmas hit the third 3.
"He can do that. He can get on fire like that," Dunphy said.
Christmas was so hot, he said he thought every shot he attempted would go through the hoop. He certainly had to impress the 19 NBA teams that sent scouts.
"They got a real show of what an NBA 2 guard can do when he gets going," Pearl said.
The Volunteers had nothing left. Christmas - trying to win three straight A-10 scoring titles - hit 3-pointers Nos. 6 and 7 and made it 82-59.
All Pearl and his players could do was listen to those derisive chants.
"We're ranked too high," Pearl said. "We have a long way to go."
The Owls knocked off a top 10 team for the first time since former coach John Chaney led them to a win over No. 6 George Washington in the 2006 Atlantic 10 tournament. He retired at the end of that season and Dunphy left Penn to succeed him. Dunphy got the Owls into the NCAA tournament for the first time since 2001 last season and now has a win he hopes can build to another tourney bid.
"Whether or not it's a watershed moment for us or not will be determined later on," he said.
