Alessandro Del Piero was just one of many Juventus fans who hadn't seen it coming.
He knew Ajax were good, that they played a bold style of attacking football. But he still expected Juve to progress to the semi-finals of the Champions League at the Dutch side's expense.
Instead, the Old Lady was left embarrassed, beaten 2-1 in her own backyard by a group of players that looked not just younger and fitter, but smarter and braver.
"I wouldn't talk up the physical aspect too much because what impressed me most is how Ajax controlled the pitch," the Juve icon told Sky Sport Italia after the quarter-final second leg in Turin in March.
"Lads of this age obviously have a system of play, a knowledge of their game, that allows them to play with total freedom of expression.
"It was the way in which Ajax set up and moved the ball that wore out the Juve players."
The hosts were, thus, left in a state of shock; "confused" by what had just happened to them, as Del Piero put it.
Fabio Capello, though, wasn't surprised. He'd already seen Juve bamboozled by such a side.
"Against Ajax, Juve suffered in the same, identical manner as they had in getting knocked out of the Coppa Italia by Atalanta [in January]," the former AC Milan boss pointed out.
"We can say that everything started there, because [Gian Piero] Gasperini's side defend one on one, and Juve are not used to that same level of pressing for the entire game.
"We should speak about and eulogise Ajax, and rightly so, but against Atalanta the same thing happened to Juve.
"Both teams counter with the ball on the ground, they attack the whole field with many men and they don't leave you space.
"What we have seen here in Turin already happened in Bergamo."
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Indeed, on that bitterly cold winter's night at the Stadio Atleti Azzurri d'Italia, Atalanta didn't just end Juve's bid for a fifth successive Coppa Italia, they obliterated it, triumphing 3-0 in a sensationally one-sided quarter-final.
As winger Papu Gomez later revealed, while they have always been a united group of players – "I spent more time with these guys than my own family" – a home draw with Roma three days previously had been key.
Atalanta had trailed 3-0 at the break to the Giallorossi but came storming back to salvage a point. After that, anything seemed possible to Gasperini's men – even a victory over a Juve side chasing a fifth consecutive domestic double.
Since then, Atalanta have lost just twice in all competitions and an 11-game undefeated run in Serie A has propelled them into fourth place in the table, three clear of AC Milan and Roma with two rounds remaining.
Champions League qualification is now suddenly a very real prospect for a team that club president Antonio Percassi has admitted would have been overjoyed with a Europa League place at the start of the season.
The latter goal will be realised on Wednesday night should they defeat Lazio to claim their first Coppa Italia – and major trophy of any kind – since 1963.
The Biancocelesti will have home advantage, with the game set to be staged at the Stadio Olimpico, but it didn't do them much good when they hosted Atalanta in the league 10 days ago.
Lazio, themselves chasing a top-four finish, took the lead after just three minutes through Marco Parolo but Atalanta bounced back to record a crucial 3-1 win.
Nobody was the least bit surprised.
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Jurgen Klopp recently called his remarkable Liverpool side "f*cking mentality giants" but Gasperini is just as awestruck by his players' resilience; they have been just as relentless as the Reds this season.
“This team is extraordinary in terms of mentality," the 61-year-old enthused after watching his side come from behind to beat Lazio just seven days after doing likewise at second-placed Napoli.
"The rest comes later, tactically, physically, but the psychological level is so important. I see every fear and doubt disappear in that dressing room and we focus entirely on winning the game."
Gasperini deserves a significant share of the credit for his players' fearlessness.
He may not be fondly remembered at Inter – sacked after just four games of the 2011-12 Serie A season for his stubborn (or admirable) refusal to abandon his preferred 3-4-3 formation – but there are few braver coaches in the game today.
He wasn't always so adventurous, though. Gasperini freely admits that for a decade of his coaching career, "retaining numerical superiority in defence was a dogma".
However, ahead of a game against Juventus during his second stint at Genoa between 2013 and 2016, he decided to go one-v-one at the back.
"I gained a spare man that I could commit to tactical manoeuvres," he told the Gazzetta dello Sport.
"It was worth the risk. The Atalanta defenders you see attacking constantly today were born from that intuition."
The results have been spectacular. Atalanta are the best team to watch in Italy. They are also Serie A's top-scorers, with 73 goals – four more than champions Juve.
At 28, and after spells at Napoli, Udinese and Sampdoria, Duvan Zapata is enjoying the most prolific season of his career, while wingers Papu Gomez and Josip Ilicic – both 31 – have been reborn under Gasperini, who has also played a pivotal role in turning Gianluca Mancini into one of Serie A's best defenders, as well as bringing through academy product Musa Barrow.
This is not even the first great team he has built since arriving in Bergamo in 2016 either.
Atalanta finished fourth at the end of his debut season with a side containing Mattia Caldara, Andrea Conti, Leonardo Spinazzola, Bryan Cristante and Franck Kessie – all of whom subsequently secured big-money moves to 'bigger' clubs in Italy.
And yet while the players have changed, Gasperini's philosophy has not – and that has been key to their continued success. As Hans Hateboer argued, they are still playing 'the Ajax way'.
“It’s true," the Dutch full-back insisted. "We both play with one-on-one situations all over the pitch.
"Ajax have more quality – just look at what they've done in Europe – but we share the same principles of football.
“I was just talking to [Ajax captain] Matthijs de Ligt about that when we were on international duty. I am not surprised by their results."
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But Gasperini insists he's not surprised that Atalanta have also upset many far richer rivals this season: "Economic considerations are one thing, but sport is another."
And Atalanta's sporting project is among the most impressive in Italy.
They have long boasted one of the best academies in the country, thanks in no small part to former director Mino Favini, who sadly passed away last month, and their continued success in producing top-quality players has allowed them to not only recruit well in the transfer market but also put money towards the redevelopment of their own stadium.
Indeed, that work has already begun, meaning their ground was closed for last weekend's 'home' win over Genoa, which was staged at the MAPEI stadium.
After the midweek Coppa showdown with Lazio, Atalanta will then face a trip to Turin to tackle Juventus in the league before wrapping up their campaign in Reggio Emilia against Sassuolo, the owners of the MAPEI, meaning they will effectively end their season with three consecutive away games.
Not that they will be daunted by the challenge. Gasperini will approach each road game in the exact same way: "I firmly believe you are more likely to get good results if you play good football."
It's certainly the best way to win hearts. Some 20,000 Atalanta fans are expected to descend upon the Olimpico for the Coppa final.
Percassi enthused, "Basically, half of Bergamo is going to this final!"
So, Lazio will see them coming. Whether they will be able to stop them, though, will be another story altogether.