No matter how many years it's been, the memories don't fade for former defensive backs.
For Kentucky Coach Mark Stoops, it came against Kansas State.
"I bobbled it about three times," he recalled from his playing days at Iowa. "I had an easy pick for a touchdown. I batted it to myself three or four times. Maybe, I wasn't fast enough to run it in. I got caught."
For Cats cornerbacks coach Derrick Ansley, it was against Missouri.
"One of our corners tipped it, and I had a clear path to the end zone, and I looked downfield before I caught it, and I dropped it right next to the sidelines," he recalled of his playing days at Troy.
It's the one ball, the one pick you knew you could return for six points, but then fate intervened.
"Every (defensive back) in America, whether it's high school, college or the pros, has dropped one they should've had," Ansley said.
For UK's Fred Tiller, it was at Florida. He took his eyes off a throw headed right for his numbers. He stopped watching for a split second, distracted by all of the green grass between him and the end zone.
"I know I've gotta take it to the crib," Tiller remembered thinking at The Swamp. "I've gotta six it."
The ball bounced off the Cats cornerback's chest and into the arms of the Florida wide receiver, who carried his good fortune to a 33-yard gain.
"It's one of those things you don't think will happen to you until it happens," Ansley said of Tiller's mistake. "Then it will never happen to you again.
"It was a good lesson. The good news is he was in position to make it and next time he's gonna make it."
The Kentucky secondary has had more than its share of lessons learned in the two seasons since Stoops took over, being ridiculed for managing just three interceptions (just one for the defensive backs) last season, tied for worst in the nation.
The Cats were lowest in the Southeastern Conference and among the worst in the country in passes defended (31) last season.
Now, thanks to lessons learned — sometimes painfully, as Tiller discovered at Florida — Kentucky's secondary is among the best in the nation at defending the pass.
The Cats are second in the league in passes defended (33) behind only Mississippi State. They are fourth nationally in interceptions with nine — which is three times their total from last season only five games into the season — and 13th in passing-efficiency defense.
"The corners have made a lot of progress," defensive coordinator D.J. Eliot said recently. "They are covering man-to-man much better. And we haven't given up that many deep balls. They've been sound on a lot of deep balls, and I'm pleased with that."
It has come from improved talent — including the addition of junior-college safety A.J. Stamps, who has as many interceptions this season as UK had all of last season — but it also comes from gaining experience and focusing on fundamentals.
"We've got a lot of eyes on the secondary and ... we hold them accountable," Ansley said. "They're up to the challenge and they're getting better every day."
Kentucky's run defense struggled last week against South Carolina, but the Cats were able to get a pick-six (from defensive end Alvin "Bud" Dupree, no less) to go ahead.
UK's run defense might get a bit of a reprieve this week against a Louisiana-Monroe team that is among the worst in the nation in rushing, averaging just 86 yards a game.
But the Warhawks' offense might be a new challenge for the Kentucky secondary, with quarterback Pete Thomas throwing for 1,159 yards and five touchdowns. Of his 197 pass attempts, he has been intercepted only twice this season.
Historically, though, Thomas has struggled to always put the ball where it needs to go. The transfer, who was at Colorado State and North Carolina State, has thrown 32 career picks compared to 27 touchdown passes.
The development of the secondary this season has been a huge boost for the Cats.
Senior safety Ashely Lowery has two interceptions this season, both at key times in the fourth quarter against Vanderbilt and South Carolina.
Stamps is 13th nationally and third in the SEC in interceptions. He's the first UK player to have three interceptions in five games since Marcus McClinton did it in 2008.
The UK defensive coordinator called cornerback Cody Quinn the player of the game against South Carolina for his lock-down coverage. Eliot said the Cats' corner play is one of its top positions on the defense this season.
A lot of that has come from learning through mistakes and growing as a group.
"It was just like a lot of pressure on everybody" last year, said Tiller, who is ninth in the SEC in passes defended with five, including one interception and four pass breakups.
"This year, ... everybody's locked in and playing for each other. The whole secondary has bought in."