LONDON • The expression on Jurgen Klopp's face said it all. A testing 24 hours for Liverpool, dominated by Philippe Coutinho's e-mailed transfer request, ended yesterday with the sort of injury-time equaliser that drives managers insane.

Liverpool, having fought back from 1-2 down to lead 3-2, were on course at Vicarage Road to open their Premier League season with a victory that would have brought some respite on the back of the Coutinho saga.

Instead, Klopp could only watch on with a mixture of incredulity and anger as Watford's Miguel Britos, looking suspiciously offside, bundled home from a corner in stoppage-time to grab a 3-3 draw.

Klopp was later furious that Britos was not ruled offside when the Watford defender poked home from the goal line after Richarlison's shot was pushed onto the crossbar by Liverpool goalkeeper Simon Mignolet.

"We were unlucky in the end. The equaliser was offside. It's obvious because the linesman is on the line. He needs to see it," Klopp said.

"I cannot change it. We would have had defensive areas we need to work on even if we'd won 3-2, but we were the better team. We should have won."

Watford manager Marco Silva said he had not seen whether his side's equaliser was offside.

Having declared that the club's wantaway Brazil playmaker Coutinho is not for sale, Klopp may need to strengthen his back four who looked completely at sea almost every time the home side came forward.

It was the second time that Watford scored from a set piece - Liverpool's Achilles' heel last season - and raised familiar questions about the need for a commanding figure in central defence.

Former Liverpool captain Jamie Carragher criticised the club's defensive system and pointed the finger at Klopp.

"It's the set-up from the manager," Carragher told Sky Sports. "They concede the most goals out of anyone in the top six. Nothing has changed."

At the other end of the pitch, Liverpool looked menacing once they got their act together in the second half, scoring two goals in as many minutes.

Roberto Firmino got the first via the penalty spot to haul Liverpool level and promptly set up the second for Mohamed Salah, the club-record signing from Roma.

Liverpool were dominant in that period and had enough chances to put the game to bed, yet they never looked comfortable at the back throughout, especially in the first half.

Stefano Okaka headed home from a corner to give Watford an early lead and Abdoulaye Doucoure later restored Watford's advantage after Sadio Mane had equalised for Liverpool with a superb goal.

"The first half, I wasn't too happy with. We passed but couldn't see what we actually wanted. The second half was a lot better," Klopp said. "We forgot to close the game. We defended a little deep. We have to push up."

Silva felt "it was a fair result".

"We had a very good first half," he said.

"I didn't like the first 25 minutes of the second half. We expected a good reaction but we needed to be better. We made mistakes. But we reacted well.

"Our fans pushed our players on. We need to show this attitude and commitment in all our games."

THE GUARDIAN, AGENCE FRANCE-PRESSE, REUTERS