Cast your mind back to Wednesday, May 1 at the Camp Nou.Barcelona led Liverpool 3-0 in the first leg of their Champions League semi-final clash.Liverpool had a corner as they desperately looked for that all-important away goal.In fact, they were so desperate that Jurgen Klopp urged Alisson to go up for the corner.“Jurgen’s pointing at Alisson to get in the box as well, and Alisson just said no to him!” Steve McManaman explained in commentary.

“Now he’s going. He’s been told no again. Salah said no to him this time.”

While journalist James Nalton tweeted at the time: “Alisson nearly went up for that corner at the end. Reached half way then changed his mind.”

Pretty much every other Liverpool player had headed into the Barcelona box to attack the ball.

But Gerard Pique headed the ball away and Barca were on the break in the 97th-minute.

It was Ousmane Dembele, Lionel Messi and Pique vs Andy Robertson and Jordan Henderson.

The home side played it perfectly as Messi teed up Dembele, who was surely about to kill off the tie once and for all.

But, incredibly, the £135.5 million signing scuffed his shot straight at Alisson.

Messi collapsed on the floor but nobody could have known the implications of that awful miss.

In fact, you can say it’s been the catalyst for this recent Liverpool dominance.

Of course, we all know Liverpool produced an incredible comeback to win 4-0 in the second leg to progress to the final.

That faint slice of hope they had entering that second leg would have vanished - especially with Salah and Roberto Firmino injured.

You can argue that Liverpool would have still won 4-0 and forced the match into extra-time but would they have had that belief that they could reach the final if they had lost by that scoreline in the first-leg? It's highly unlikely. 

Of course, failing to win the Champions League means there would be no Super Cup or Club World Cup triumph for Liverpool, which have since followed this season.

And then there’s the momentum which Klopp’s side have taken into their Premier League campaign, in which they currently sit 13 points clear with a game in hand.

There are plenty of ‘what-if’ moments in the history of football but it’s impossible to feel Dembele’s miss was a huge sliding doors moment for Liverpool.