Davidson, the No. 13 seed, hit only four of 19 3-point attempts and ended up shooing 35 percent from the floor (21-of-60), well off its average of 44 percent. . , off their average of 44 percent.
Jake Cohen had 24 points and 10 rebounds for Davidson, which made the tournament for the 11th time but first since 2008 when Stephen Curry led long-shot Wildcats to the round of eight.
Cohen found openings, but it wasn't easy.
"It's something that's always in the back of your head," he said. "When you get the ball out you've got to be worrying about their pressure and how you're going to break it."
Siva, who masterfully worked off screens, had 17 points and six assists for the Cardinals (27-9), who made it through their opening round game for the first time in three years.
Chane Behanan added 14 points and 11 rebounds for the Cardinals, who led by as many as 14. Louisville will play Saturday against the winner of Thursday's game between New Mexico and Long Beach State.
The Cardinals jumped out to the early lead but Nic Cochran hit a 3-pointer to give Davidson a 13-12 advantage. Kyle Kuric's layup put Louisville back in front.
Louisville's 6-foot-11 center, Gorgui Dieng, got into foul trouble, picking up three midway through the first half. But the Cardinals began to inch away, pulling ahead 20-16 after Behanan's layup and Kuric's jumper.
Davidson fought off Louisville's defensive pressure and narrowed it to 26-24 on 6-10 junior Cohen's turnaround jumper with 3:20 left in the half. But the Cardinals slowed down the Wildcats and went up 31-25 after Russ Smith's 3-pointer with 1:09 left.
Cochran made a free throw before Elisha Justice's layup with 21 seconds left that made it 33-25 at the break.
Siva opened the second half with a dunk to stretch the Cardinals' lead to 10 points. His jumper with 14:20 left extended the lead to 43-31.
Behanan's layup put Louisville up 58-44 with 3:37 left. Davidson got to within 59-51 when Chris Czerapowicz made a 3-pointer with 1:57 left. Cochran made three straight free throws to make it 67-60 with 22.6 seconds left.
Tyler Kalinoski's layup got the Wildcats within 67-62, but time ran out for Davidson.
McKillup said the lack of tournament experience hurt the Wildcats.
"The hardest thing I felt in terms of this team for this particular game was the lack of NCAA experience," he said. "I think they showed themselves very well. For being their first time in the NCAA tournament, I was incredibly pleased with the way they handled themselves. They were superb.
"You saw there at the end, we didn't quit. We didn't give up. We used every ounce of energy to make every play count and try to stay in the game."
The Cardinals were ranked as high as No. 4 earlier this season, but a spate of injuries and a stretch with five losses in seven games dropped them out of the rankings. They came into the Big East tournament with losses in three of their four final games.
But they rolled through the conference tourney with four wins in four days, beating Seton Hall, Marquette, Notre Dame and, finally, Cincinnati in the championship game to take some momentum going into the NCAA tournament.
Davidson got a tournament berth this year with a dramatic, double-overtime victory over Western Carolina last Friday in the championship game of the Southern Conference tournament. The Wildcats led by 12 with 2 minutes left in regulation but needed two overtimes to put it away.