Liverpool played a 1-1 draw with Athletic Bilbao on Sunday in front of 40,000 fans at Anfield.
The home crowd were loud and boisterous after a long stint away from the ground.
And it was perhaps no coincidence Liverpool were able to take an early lead through Diogo Jota.
The Portuguese took a pass from Sadio Mane before drilling a low left-footed shot into the far corner.
But Liverpool were unable to capitalise on their first-half dominance, and instead allowed Bilbao back into the game, with Alejandro Berenguer equalising for the visitors eight minutes into the second half.
Reds fans would have been delighted to see saw Virgil van Dijk start and play around 70 minutes.
However, an injury to Andy Robertson put a damper on the evening, with the Scotsman limping off late in the first half after blocking a cross.
Klopp told his post-match press conference: "We obviously don't know in the moment how serious it is. It was pretty painful and that's why Andy went off. You probably saw it on the TV pictures better than we did, but he got the ball, the ball on the front of his foot, [and] twisted the ankle.
"The pain settled already, but we cannot say anything further without further assessment tomorrow. He has to get a scan and then we will know more."