Jurgen Klopp warned that Liverpool must remain “on alert” despite putting one foot in the Champions League final with a dominant 2-0 win over Villarreal in the first leg of their semi-final tie at Anfield on Wednesday.

Two goals in two minutes undid Villarreal boss Unai Emery’s defensive game plan as Pervis Estupinan deflected Jordan Henderson’s cross into his own net before Sadio Mane slotted in a second.

The Reds remain on course for an unprecedented quadruple of Champions League, Premier League, FA Cup and League Cup.

And barring a huge upset when the sides meet again in southern Spain in six days’ time, Liverpool’s season will finish with a third Champions League final in five seasons in Paris on May 28.

“It is 2-0 at half-time,” said Liverpool boss Klopp. “You have to be completely on alert, 100 percent in the right moment and play the second half like we played the first. We know it will be a tricky atmosphere for us.”

Title-chasing Liverpool will play two Premier League games in the final week of the campaign after their match against Southampton was rescheduled due to their participation in the FA Cup final.

Klopp’s men will travel to the south coast for their penultimate fixture of the league season on Tuesday, May 17, three days after their date at Wembley with Chelsea.

Quadruple-chasing Liverpool, who already have the League Cup in their trophy cabinet, are going head to head with reigning champions Manchester City for the title.

Guardiola’s men face a tough trip to West Ham on May 15 and conclude their season a week later at home to Aston Villa, while Liverpool host Wolves on the final day.

Liverpool and City could also meet in the final of the Champions League if both win their semi-final ties.