(REUTERS) - Liverpool manager Juergen Klopp said the Covid-19 outbreak which forced the postponement of their League Cup semi-final, first leg against Arsenal last week included many false positives, with Trent Alexander-Arnold the only confirmed case.

The Reds had asked the English Football League to reschedule the game last Thursday due to a "severe outbreak". Alisson Becker, Roberto Firmino and Joel Matip returned positive tests, while Klopp also tested positive during the previous weekend.

Liverpool beat third-tier Shrewsbury Town 4-1 in the FA Cup third round on Sunday (Jan 9), with Klopp returning to the dugout. He had to field four teenagers in the starting line-up.

"We had last week a proper outbreak and it showed up that we had a lot of false positives but the rules are like they are, so all these players who are false positives couldn't play," Klopp told reporters.

"The only real positive came from Trent Alexander-Arnold and all the rest were false positives."

Midfielder Fabinho scored twice while Kaide Gordon and Firmino also scored as Liverpool came from a goal down to advance into the FA Cup's fourth round.

They host Arsenal in the League Cup semis on Thursday before the return leg on Jan 20 at the Emirates Stadium.

Klopp also dismissed talk that the Reds could be without injured midfielder Thiago Alcantara for the rest of the season.

The Spaniard has not played since their 3-1 Premier League win over Newcastle United on Dec 16 after picking up a hip injury.

"He is not out until the end of the season, not at all," Klopp said.

"It (the injury) is around the hip, that's the situation and it needs time. He didn't train this week but we expect him to be back to do rehab stuff from tomorrow on and then we will see."