Alonso was strechered off injured during Sunday’s 3-0 victory over Newcastle Utd at Anfield after being the victim of a vicious challenge by Joey Barton.
It was first thought Alonso’s injury wasn’t too serious, but now Benitez isn’t confident he will be travelling to London with the rest of the squad for the 5.30pm kick-off at Upton Park.
He told the club’s official web site, “Xabi is the main doubt for the weekend. He has been working and hopefully he will be better in a few days. He is improving but we have to wait.”
But Benitez does expect to have striker Fernando Torres, who missed the Newcastle game with a hamstring injury, and midfielder Javier Mascherano, who also took a knock on Sunday, available.
On Torres, Benitez continued, “He is training with the physios and maybe tomorrow he will start training with the rest of the team. I think he will make the weekend.”