Georginio Wijnaldum an injury doubt for Club World Cup

Resources are already stretched thinly, with a youth team set to play a Carabao Cup quarter-final at Aston Villa on Tuesday, and with Fabinho (ankle) and Joel Matip (knee) ruled out of games in the Middle East, Klopp can ill-afford another absentee.

"With the Gini injury, Dejan three or four days ago, our squad is not getting bigger. That is not cool," he said.

"But that is the same problem if we go to Aston Villa in the Carabao Cup quarter-final."

Asked whether the Holland international could travel, Klopp added: "That is actually in the moment one of my smallest concerns – he could probably fly – but my problem is more what exactly the injury is and I don't know that yet.

"It is a muscle thing and you never want that for a player. In these moments it immediately makes it more difficult."

Wijnaldum's injury was the only cloud on a day when Mohamed Salah took his tally to four goals in his last three matches, and 13 for the season, with a brilliant double.

First he finished off a counter-attack from a Watford corner with a superb right-footed shot over goalkeeper Ben Foster and then completed victory in the 90th minute by backheeling in substitute Divock Origi's mis-directed shot.

It was not a straight-forward victory, unbeaten Liverpool's 16th in 17 league matches this season, as Watford had three decent chances in the first half.

Troy Deeney, Abdoulaye Doucoure and Ismalia Sarr all missed, with Alisson Becker producing two good saves early in the second half.

Defeat left Watford rooted to the foot of the table on nine points, six from safety, having managed just nine league goals in 17 games.

New manager Nigel Pearson took encouragement from his first match in charge, however.

"What we have to do, all of us as staff, is to work with the players to help them find the belief themselves, we can't give them that," he said.

"We hopefully help facilitate that and give them the framework to do that but ultimately players have to go out on the field and play and they played with a lot of conviction (at Anfield).

"It's absolutely required for us to find a way of getting out of the situation we are in – and it is do-able. We are capable but we have to start making it happen."