Mauricio Pochettino conceded Chelsea may be forced back into the transfer market for attacking reinforcements following the injury to Christopher Nkunku.

The France international, signed in the summer from RB Leipzig, was one of the standout successes of the team’s pre-season tour of the United States with three goals in his five games, but sustained a meniscus injury to his knee against Borussia Dortmund in Chicago and is unlikely to play again before December.

The 25-year-old underwent surgery this week and has begun his rehabilitation but it is understood that the club expect a 16-week recovery period, rendering the need for added attacking options suddenly more urgent.

Chelsea registered their lowest goalscoring return in almost a hundred years last season with just 38 Premier League goals, and there had been optimism that in Nkunku and fellow new signing Nicolas Jackson a solution had been found.

It is understood there is no update on the future of out-of-favour striker Romelu Lukaku, who was pictured at Cobham in a Chelsea tracksuit this week despite having made clear his desire to return to Italy where he spent last season on loan at Inter.

With Pierre-Emerick Aubameyang having departed and Armando Broja recovering from injury, it leaves Jackson as the club’s only recognised striker available for Sunday’s Premier League opener against Liverpool.

“We feel sorry about (Nkunku) because he was doing well,” said Pochettino. “He was an important player for us, his quality is there, one of the best offensive players, can play in different positions.

“It’s a big issue for us. But now it’s about not thinking too much about the injuries, and being positive.

“We’re working on the market also because we’re going to miss one player like this, offensive. The club is working to try to find a solution, maybe short-term, maybe long-term, to add the right profile.”

Pochettino would not comment on Chelsea’s pursuit of Moises Caicedo, insisting on the need to be respectful of Brighton whilst the clubs remain locked in a standoff over their valuations of the player.

Jurgen Klopp confirmed on Friday that Liverpool have agreed a deal with Brighton for the midfielder, believed to be a British record in the region of £110m, but Caicedo is understood to favour a move to Stamford Bridge.

Chelsea’s third and most recent offer was £80million, well short of what owner Tony Bloom believes the player to be worth.

Liverpool and Chelsea endured hugely disappointing campaigns last season and started the summer in significant need of squad renovation, though success so far in the transfer market has been mixed.

The Reds have made just two first-team signings, with Caicedo’s former team-mate Alexis Mac Allister having joined alongside Hungarian midfielder Dominik Szoboszlai, whilst Chelsea have undergone a more comprehensive overhaul with over £180m spent on six signings.

Pochettino said he believed the rebuild his club faces is more challenging than the one Klopp is dealing with at Anfield, made tougher in part by the recent high turnover in personnel.

However, he added that he would not allow his players to use it as an excuse on Sunday.

“I think we are more in transition than Liverpool,” he said. “Because I am new here, and Klopp is for seven years at Liverpool. In seven years you can anticipate the transition, you can see what is going to come, you can be ahead of the problems.

“Of course, we are Chelsea, the history of the club is to win, even if we are in transition, people know we cannot give the message that we are in transition. We need to win and we need to be ready to win. And we are going to be ready win against Liverpool.

“The mentality for the players and the whole club is about how to compete in the best way to be strong and to really believe in us. I’m not going to accept a different way to think.

“Excuse? OK, for other people, but no excuse for us, because we need to be strong.”