Ty Johnson appeared to send the game to double OT on his tying layup for Villanova off a missed UConn free throw. But Napier, who questioned the heart of his teammates after a loss Saturday at Marquette, hit the pull-up 3 and got all net in the final ticks to keep the defending champion Huskies' NCAA tournament hopes alive.
The Huskies (17-10, 7-8 Big East) rallied from an 18-point deficit to win without coach Jim Calhoun on the bench. Calhoun should return from a back injury and be on the sidelines for Saturday's game against No. 2 Syracuse.
Lamb was 11 of 21 from the floor to rally UConn against the Wildcats (11-16, 4-11), who were led by Dominic Cheek with 23 points.
Andre Drummond had 11 rebounds and four blocked shots for the Huskies. UConn overcame a dreadful start from the floor and a brutal 10 of 21 effort from the free-throw line.
Johnson added 14 points for Villanova, and JayVaughn Pinkston had 13 points and 10 rebounds.
Leading scorer Maalik Wayns sat out for Villanova with a sprained MCL in his left knee, and guard James Bell was out with a sprained left ankle.
Each team made clutch plays in the final 2 minutes of regulation only to throw in a few silly ones, as well. Mouphtaou Yarou put Villanova ahead 60-58 with 2:18 left with two free throws. Ryan Boatwright, a 73 percent free-throw shooter for UConn, missed both of his attempts from the line with 1:05 remaining.
The Wildcats might have been able to hang on after their next possession, but Cheek's inbound pass was picked off by Roscoe Smith and Alex Oriakhi converted the tying layup. That made it 60-all with 23 seconds left.
Pinkston airballed the potential winner and Villanova headed to overtime for the second straight game.
Lamb snapped a tie game in OT with a 3-pointer and the Huskies kept the lead until Johnson's layup gave the Wildcats the clutch bucket they needed to tie the game in the final seconds.
It just wasn't enough.
Calhoun missed his ninth game this season, three because of an NCAA suspension for recruiting violations and the last six after taking an indefinite medical leave with spinal stenosis. The school has said Monday would be the last game he would miss. Spinal stenosis is a narrowing of the spine, normally associated with aging and sometimes with arthritis.
He surely loved this comeback.
The Wildcats squandered an 18-point lead in a loss to Marquette last month and wasted a 20-point edge in an overtime loss to Notre Dame on Saturday.
Villanova didn't wait until the second half to let the collapse start against UConn.
Behind a pair of early 3s from Cheek, the Wildcats stormed to a 26-8 lead, giving them a chance to either crush the opposition for once or blow the lead again.
The Wildcats blew it.
UConn closed the half on a 22-4 spurt, tying the score at 30-all on Drummond's tip-in right before the half ended. The Huskies missed 10 straight shots - and 15 of their first 20 overall - before closing on an 8-for-15 run. They missed their first seven 3-point attempts, but Boatwright and Napier each hit one during the game-changing run to close the deficit.
The winning buzzer-beater came in front of a lethargic crowd of 13,832 fans.
Six years ago, they played the most memorable game in their rivalry.
The Wildcats were No. 4 in the poll when they beat top-ranked UConn 69-64 on Feb. 13, 2006 in front of 20,859 at the Wells Fargo Center, the largest crowd to watch a college basketball game in Pennsylvania history. Villanova fans stormed the court to celebrate the Wildcats' first win over a No. 1 team since Feb. 18, 1995, when they beat Connecticut.
Times have changed in a game between the defending national champs and Villanova, a program that reached the Final Four in 2009. The Wildcats lost their third straight game and for the sixth time in seven games.