The University of Louisville junior scored 16 points - the biggest two on a shot-clocking beating jumper with 45 seconds to play - and grabbed 11 rebounds to lead the Cardinals to a 69-63 win over top-ranked, and previously unbeaten, Pittsburgh in front of 20,082 fans at Freedom Hall on Saturday night.
"My 21st birthday, beating the No. 1 team, it doesn't get any better than this," said Clark, who also had three blocks, three assists and two steals.
Clark, and the rest of his teammates, overcame a slow start as the 20th-ranked Cards (13-3, 4-0 in the Big East) won their third straight game over a Top 20 team.
"You guys may not believe me, but I would've been proud of our guys if we would have lost," UofL coach Rick Pitino said to start his post-game press conference. "I thought our guys played with tremendous effort and tremendous heart."
"That's how you wish somebody a happy birthday," Williams said. "(Edgar) Sosa just had a birthday the other day (he turned 21 on Jan. 15) and Earl today, so we wished them both a happy birthday."
However sophomore center DeJuan Blair, who entered averaging 14.7 points and 13 rebounds, scored nine points and grabbed 10 rebounds in only 20 minutes due to foul problems, and senior point guard Levance Fields scored just eight points, on 3 of 14 shooting, and had six turnovers.
The Panthers, who came in having won their first 16 games by nearly 20 points, looked the part of the top team in the country early in the game.
Pitt was torrid from three-point range, hitting five of its first six from long range, as the Panthers pulled out to a 20-7 lead a little more than six minutes into the game.
"They threw the first punch, but we survived it," said Williams, who also grabbed seven rebounds and dished out four assists.
UofL got back in it with an 11-0 run. Williams scored seven, and Samuels four, in the spurt that saw UofL take its first lead (24-23) with 6:19 to play in the first half.
However, the Cards scored just one point the final 4:06 as they trailed 32-30 at intermission.
UofL shot just 29.4 percent in the first half, including 1-for-9 from three-point range (11.1 percent). Clark mirrored his team's struggles, going 2 -for-10.
"Nothing was going in, it was an off night, but I couldn't catch a break," said Clark, whose team held a 26-18 rebound advantage at halftime. "But I didn't get discouraged."
On the flip side Pitt, which came in averaging 6.3 made threes per game, was 7 of 11 (63.6 percent) from long range.
At halftime UofL's 1982-83 Final Four team was honored, but at the start of the second half it was Pitt that played like a team destined for Detroit (site of this season's Final Four).
The Panthers went on a 7-0 spurt to take a 41-35 lead before the Cards fought back to within 48-45. But Pitt responded with another 7-0 run to push its lead to 10 (55-45) with 8:55 to play.
UofL answered with a 9-0 run to cut the Panthers' lead to one. The Cards still trailed, 58-54, with five minutes to play before UofL reeled off 10 straight points. The run was capped by Clark's 17-foot jumper just before the shot clock expired with 45 seconds to play.
"He couldn't hear me, but I was yelling, 'Shoot, shoot, shoot,'" said Pitino, who after the game gave Clark a hug at midcourt as the two prepared for an ESPN interview. "That was a big play. We made great plays down the stretch."
Pitt, meanwhile, struggled at the end. The Panthers hit just one field goal in the final 8:54.
"Give them credit, they beat us," Pitt coach Jamie Dixon said. "We played well, they played well. They made shots down the stretch. We obviously had to battle through some foul difficulties. We had to struggle through that. We talked about staying out of trouble and that was the difference."
UofL hit 5 of 6 free throws in the final 16.6 seconds to seal it. The Cards shot 54.5 percent (12 of 22) in the second half, including 5 of 7 from three-point range. Pitt, meanwhile, shot 30.6 percent (11 of 36) in the second half, and missed 12 of its 15 three-point tries.
UofL next travels to Rutgers at 7 p.m. Wednesday.
"We're not done yet, until we hold up that championship trophy, we're not done yet," Williams said.