Rafael Benítez has shown the first signs of exasperation with Alberto Aquilani by suggesting the Liverpool midfielder's latest problem is not merely physical but psychological.

The Italy international has started only eight times for Liverpool since his ¤20m arrival from Roma and is sidelined with an ankle injury sustained in training on Wednesday. Aquilani has complained of discomfort in the same ankle that required surgery last May and which forced him to miss the first three months of this season, although scans have so far failed to identify the cause of the problem. Benítez admits he is at a loss as to when the 25-year-old will be fit but indicated that a history of injury problems is affecting Aquilani.

"He was complaining of pain in his ankle and said he couldn't train," the Liverpool manager said. "We will have to talk with the doctors to see what's going on because at the moment we don't know."

There are concerns that the Italian, ear-marked as the natural replacement for Xabi Alonso in a season that opened amid high expectation at Anfield, will be absent for the rest of this campaign should he undergo exploratory surgery. But Benítez said: "We don't know if he needs an operation. He has some pain and we will just analyse that with the doctor. It's the same ankle he did before. Some players maybe can manage with the pain, some players when they have pain cannot. When you talk of pain you never know, it depends on each individual and that makes it really difficult."

Another Liverpool midfielder aggravating Benítez is Albert Riera, whose proposed move to Spartak Moscow has stalled over his demands to be paid almost double what he earns at Anfield. The Spanish winger effectively announced the end of his Liverpool career when he spoke out against Benítez and the club last month, having become marginalised and adamant he had to move to salvage a World Cup place.

Liverpool were "a sinking ship", according to an interview Riera gave to a Spanish radio station, only to be described by the player this week as "one of the best clubs in the world" following Spartak's refusal to offer over £60,000 a week in wages. The U-turn represents a further headache for Benítez, who sent Riera home from training three times for poor behaviour before his radio outburst and, contrary to the midfielder's claims of aloofness from his manager, spoke to the £8m signing on several occasions.

Benítez was told a deal to take Riera to Russia was in place before the player went public with his criticism and, though a permanent transfer to CSKA failed to materialise and the Spartak loan has stalled, he still hopes an exit can be arranged before their transfer window closes next week.

"We still have some time until the end of the Russian transfer window so we will see what happens," he said. "I didn't see his latest comments but for me, when he was talking this way on the day before a massive game [against Lille] was disappointing. It was especially so when he was saying things that weren't true, so I was really surprised. He also said he wants to play, that's why he had to go, but our fans are not stupid and they will know what's going on. We'll see what happens now."

Benítez he will consider the fitness of Fernando Torres and Steven Gerrard before finalising his starting XI at Birmingham City tomorrow. The influential duo were substituted due to tiredness against Benfica on Thursday, when Liverpool played for over an hour with 10 men, and with the pitch at St Andrews attracting criticism from Arsène Wenger last week, the Liverpool manager is wary of its potential impact.

He said: "It's always difficult when the pitch isn't good enough, so we will have to see. After a couple of days rest we will check with the players and see how each one is. If we have to rest someone we will see because we want to keep the performance at the same level."