The extent of the knee injury suffered by the Liverpool midfielder during the first leg of their Champions League semi-final against Roma in April has now been revealed.

The 24-year-old sustained what has been described as multiple ligament damage in a tackle and underwent successful surgery eight days later.

He will not need to go under the knife again but faces a long rehabilitation programme before he will be able to return to action.

A statement from Liverpool read: “The estimated length of his lay-off was not revealed at the time at the request of Oxlade-Chamberlain, who did not want the news to distract from the Reds’ ongoing Champions League run and the excitement surrounding it.”

The news will come as a huge blow and a shock to Liverpool fans, with Oxlade-Chamberlain among their star performers during the latter stages of last season.

Manager Jurgen Klopp said: “It feels like now is an appropriate time to tell people that for Ox this coming season will be about focusing on recovery and rehab.

We have known this from pretty much the day after he got the injury and after the successful surgery, we were sure of it. His recovery has started superbly well. If we do see him back this season it will be a bonus.

Oxlade-Chamberlain brought to an end a six-year stay at Arsenal by joining Liverpool last summer in a £35m (€39.3m) deal.

Strengthening his midfield has been one of Klopp’s main priorities in the transfer window so far, with Naby Keita, Fabinho, and Xherdan Shaqiri all arriving at Anfield.

And Liverpool are closing in on a €75m world-record deal for Roma goalkeeper Alisson after agreeing to meet Roma’s valuation of the Brazil international.

The current record transfer in pounds for a goalkeeper is the £35m (€39.3m) paid to Benfica by Manchester City for Alisson’s compatriot Ederson last summer, while the highest price in euros was Gianluigi Buffon’s €53m move to Juventus back in 2001.

Klopp has given public backing to Loris Karius following his calamitous Champions League final performance but has made signing a goalkeeper a priority.

The club are not prepared to say anything publicly until the deal is completed and as yet no medical has been arranged, with the possibility remaining that another club could match Liverpool’s offer.

Chelsea have also been linked with the 25-year-old, who began his career with Internacional before moving to Roma two years ago.

Italian website Forza Roma, which is affiliated to newspaper La Gazzetta Dello Sport, published a video which it said showed Alisson at Rome’s Ciampino airport. It said he was preparing to board a private jet to Manchester and was on his way to Liverpool for a medical on Saturday.

Alisson spoke in the video, saying: “Greetings to Roma fans. I’m sorry but I cannot say any more, I’ll say everything later.”

For his part, Klopp insists his players will welcome the help from new signings.

A hectic end to last season and a number of injuries left Liverpool’s resources thinly stretched, and the German is determined to avoid that this season.

Klopp said: “Maybe it is the first year we don’t sell a key player. There was always a lot of change, but in both directions. Now it is more in one direction. Big teams, successful teams, if you don’t buy it, you have to build it. That means stay together, bring additions in, and make the next step.

“The team and squad is in a really good moment. We had the situation where we had 12 (senior) players (fit) — they know we need the depth in the squad. It is not like they say, ‘Bring in another midfielder? Why? We are all still here’.

“They know we need the quality and they know that if we win something here then we will win it with 25 players.

In the whole period in the last two months of the season this club and this team came closer together because we had to fight like crazy. What the boys did in those last two months was exceptional.

Alisson is expected to be the final new face through the door this summer but, although he has done his business relatively early, Klopp is facing difficulties preparing for the season with those players who reached the latter stages of the World Cup having a break before beginning their pre-seasons.

Klopp said: “I love the pre-season but I really loved the good old pre-season when you had all players together and you can train from the first day.

“In this moment we miss three or four offensive players. (Roberto) Firmino, Mo (Salah), Sadio (Mane) and Shaq (Shaqiri). It means an interesting challenge. Hendo (Jordan Henderson) is not in, Trent (Alexander-Arnold) is not in, Simon (Mignolet) is not in and Dejan (Lovren) will be the latest to come back.”

Movement over the last few weeks of the transfer window is set to be away from Liverpool, with Klopp admitting others will join Jon Flanagan and Emre Can.

“Of course we have to,” he said. “We need a lot of players but not 40.”