Liverpool must find an extra gear against Manchester City in Sunday's Community Shield despite ending its pre-season slump, according to manager Jurgen Klopp.

The European champion fell behind to an early Memphis Depay penalty in Geneva, before strikes from the returning Roberto Firmino and Harry Wilson either side of a Joachim Andersen own goal secured an accomplished 3-1 win over Lyon.

The result came on the back of a 3-0 weekend loss to Napoli at Murrayfield – Liverpool's fourth winless friendly in succession.

"All round it was a much better performance, but again, I said that will happen," Klopp told his club's official website. "Now we have three more days to prepare for the City game and then we will see what we can do there."

READ| Liverpool 3-1 Lyon: Roberto Firmino scores on Reds return after Alisson error

"Man City is different to all other games that you play – you have to play a pre-season game against Man City to prepare for Man City and we didn't do that! We need to adapt to that, but all good. Today [Wednesday] was, from a physical point of view, very, very important for all the lads, and from a psychological point of view as well," added Klopp.

Firmino returned to club action alongside Alisson and Mohamed Salah following their international exploits over the close season.

"Mo is naturally fit and he can sprint all day, which us helps of course," he said. "It opens up the pitch, you can play much more football - not always between the lines. If you from time-to-time chip the ball in behind the line, then Mo makes these offers which is very important for us. Bobby in between the lines and in the box [was] present [and] really important," said Klopp.

Klopp insists the trio will be involved against City and did not rule out handing them starts.

"I don't say 100 per cent not, there's a chance that they will play, yes. They will be involved whenever, from the start, maybe we cannot make these [number of] changes like today [against Lyon] after half an hour or whatever, that's maybe not possible in that game, so we have to see," opined the Liverpool manager.

Klopp unsure about Wilson's Liverpool future

Liverpool manager Jurgen Klopp has been happy with Harry Wilson's pre-season, but he remains unsure about the attacker's future. Wilson, 22, scored a 30-yard stunner as the European champion beat Lyon 3-1 in a friendly at the Stade de Geneve on Wednesday.

READ| Alisson spells out Liverpool's plan to win 'everything'

The Wales international impressed during a loan spell with Derby County last season, scoring 16 Championship goals, and has been linked with Newcastle United, Aston Villa and Bournemouth this close season.

Speaking after the win over Lyon, Klopp said: "We are in constant conversations, that's clear. We have to do the right thing for us and for the boy."

"He is obviously a really good player and I was really happy with him in the whole pre-season. He came back from Derby in a completely different [shape]. That's a good example of how a loan can really work out – it was for Derby really good and for Harry as well. For us as well, which is good," Klopp told a news conference.

"I am happy for him that he could show that tonight again. He played not in his best position, he played left wing and did it really well. We tried to set it up a little bit so it is more comfortable for him with positioning and stuff like that. When he scored the goal, it was just Harry – brilliant," he added.

Liverpool faces Manchester City in the Community Shield on Sunday before its Premier League opener at home to Norwich City five days later.