JURGEN KLOPP HAS promised Liverpool will not under-estimate Champions League semi-final opponents Villarreal and their head coach Unai Emery.

Almost six years ago, in his first season at the Merseyside club, Klopp’s side led 1-0 at half-time of the Europa League final against Emery’s Sevilla in Basel but went on to lose 3-1.

It was the first – and only – time Emery has beaten Klopp, having lost four and drawn one during his time at the Arsenal helm.

Villarreal, last year’s Europa League winners, are bidding to reach their first Champions League final but Klopp insists the Reds will not make the same mistake as Juventus and Bayern Munich, who have already been dispatched by the Spanish side.

“It is a massive game,” said Klopp, who is bidding to lead Liverpool to a third final in five years. “So many coaches out there work their socks off their whole life and have no chance to be close to a semi-final so we have to enjoy it.

“There might have been a little advantage in the last two games. Maybe Juve or Bayern under-estimated them, but that will never happen to us.

“They are still a really good football team who wants to make history as well. It would be the first time they go to a final, which would be a massive thing to Villarreal, but it is to us the same importance.”

Klopp said he has not thought about the 2016 Europa League final defeat for a while but believes it was a significant moment, just seven months into his Anfield reign.

“I said it that night, I think that we would come back, without knowing we would come back, but at that moment I really thought we had a chance to come back stronger and we did,” he said.

“Would it have been anything different since then if we had we won that night? I don’t think so.

“I would have loved to have lifted that trophy that night but you have to learn from these things and that’s what we tried to do.”

Jurgen Klopp and Unai Emery at the end of the 2016 Europa League final. DPA / PA Images DPA / PA Images / PA Images

While Klopp may not have given that night in Switzerland much thought of late, for captain Jordan Henderson it lives long in the memory.

The midfielder was an unused substitute at St Jakob-Park as Joe Allen, Christian Benteke and Divock Origi were all brought off the bench ahead of him in an attempt to turn the game around.

“That night always sticks out,” the 31-year-old said. “I always remember it just because I can remember after the game going back to the hotel and the lads were all very disappointed and all just wanted to go back to their room, not see anyone and get your head down.

“But the gaffer was a bit different to what you expect. He got everyone together downstairs in the bar area and sort of spent the night together.

“I felt as though he knew this was the beginning, the start of something special to come. As a player, it is very difficult to think that then, when you’ve just lost the final, but I always felt he was very different to anything I’d seen before.

“He sort of knew what was coming in the next few years and I feel as though he has produced that and proven that was the beginning of something special.

“It was more difficult for us as players to see past that night at that moment because you are so devastated you have just lost a European final.

“But I felt as though the mentality was different. I felt that confidence transmitted to the players and, as days go on, you try to use it as motivation to be better and try to get to another European final, improve as a team and be successful going forward.

“The manager had a very good way of seeing the bigger picture and using that experience to our benefit going forward.

“It’s been pretty eventful since then, so hopefully we can carry on going on in the right way. (Wednesday) is a big night to continue going in the right direction.”