Liverpool lost their final pre-season friendly on Saturday, going down 2-1 to an excellent Atletico Madrid side in front of a 44,000 sell-out crowd.

Lucas Leiva scored a late goal after Argentina star Sergio Aguero and former Manchester United forward Diego Forlan had given the Spaniards a two-goal half-time lead.

The £20m new boy Aquilani, who completed a medical and agreed a five-year contract on Friday, had flown home to Italy and did not witness his new team being hit by more injury worries.

Jamie Carragher and Fernando Torres picked up ankle problems, and will be carefully monitored this week ahead of Sunday’s trip to north London.

Benitez, who has lost Sami Hyypia and Alvaro Arbeloa this summer, also has injury problems over defenders Daniel Agger, Martin Skrtel and Fabio Aurelio with which to contend.

Aquilani, who following a stringent medical was able to convince Liverpool that his ankle injury is not a long-term worry, will miss the first four to eight weeks of the campaign.

Benitez said: “Jamie’s injury is not serious, just a twisted ankle. But with our injury problems which include Daniel Agger and Martin Skrtel, we felt we needed to take him off as a precaution, just in case.

“We will keep an eye on him for two or three days to see how he reacts, but I feel he will be OK. Hopefully, Agger or Skrtel will be fit too.

“Agger has a back problem, and that should be OK in a couple of days. Skrtel is nearly over his hamstring injury, he’s nearly there.

“He is training again and I believe that at the end of this week both of them will be fit to play.

“I do not believe that the injury to Fernando Torres is anything serious, he had an ankle problem but it was a minor one and he also came off as a precaution.”

Benitez insists he always knew he would have to wait to see Aquilani fit to play.

He said: “When we were talking (to Roma) about Aquilani we knew he was recovering from an operation and would not be able to play for the first weeks of the season.

“But we can wait for him. We have enough midfield and offensive players to cope, and when he does start to play everyone will see what a clever player he is.

“Aquilani has great quality.

“We had to think about players who could make a difference for us. He is a very good player on the ball, and hopefully he can produce the sort of passes that we missed last season. Certainly at home against packed defences when we could only draw important matches.

“Alonso and Aquilani are different types, they are difficult to compare. Alonso can drop back to receive the ball and then play long passes, Aquilani plays further forward between strikers and the midfield.

“He is very clever and can pass the ball well and he is also a threat in the final third.”

Even before the injury to Carragher, Benitez revealed he had already been in talks with Hull over defender Michael Turner, having seen a £6m bid rejected.

Hull want £12m, and Benitez must decide this week whether to risk going into the season with such limited defensive resources or to bring in a new man.

On Saturday he saw youngsters Danny Ayala, Mikel San Jose and Martin Kelly all plunged into defence against the outstanding Aguero.

San Jose, in particular, discovered what a world class striker is all about. The Argentina forward’s searing pace over 50 yards stunned the young Spaniard and brought a collective gasp from the Kop.

Benitez said: “We have two options. One is to bring in someone at the back and the other option is to keep working with the young players.

“We have three centre-backs to get fit and will need one more as a fourth. We have to decide what to do. Some youngsters need the opportunity to impress, we will see how they go.”