Everton full-back Leighton Baines may need another operation on his left ankle, according to manager Roberto Martinez, who described the injury as a "disaster".
Speaking after Everton's 2-2 draw with Watford in the Premier League on Saturday, Martinez claimed Baines had looked "stronger than ever" before hurting the ankle he had surgery on in May.
Baines hurt his ankle at training on Friday and could miss over a month.
"We don't know how long he will be out for but it has been a real disaster," Martinez said.
"We were preparing for the Watford game and in training, he blocks the ball and it hits him in exactly the same place where he had surgery, with the unfortunate result that he's going to be out for a while."
Martinez was expecting a big season from the 30-year-old England international.
"It was devastating, because he had worked so hard and looked stronger than ever," the Spanish manager told EvertonTV.
"I don't think I had seen him looking as powerful and refreshed in the last two seasons. Then there was this big knock.
"We still have to find out how long it will be, but it is not going to be just two or three weeks - I think it is going to be a little bit longer than that."
Martinez also hailed the impact of Arouna Kone, who teed up Ross Barkley to make it 1-1 at Goodison Park and then scored the second equaliser himself to cancel out Odion Ighalo's 83rd-minute effort for Watford.
It was only Kone's second league goal for Everton since he arrived from Wigan at the start of the 2013-14 season, with the Ivory Coast international having struggled with a knee injury for the majority of his Everton career.
"Arouna Kone arrived at Everton and I don't know if a black cat crossed his path at Finch Farm, but everything went against him," Martinez said.
"He had a really poor injury and it was really difficult for him.
"He was never able to get the momentum or luck and nobody got to see the best of Arouna. But he took responsibility in the worst possible moment of the game today.
"When he came on the pitch, you could see he had to win the crowd over and I was delighted for him. He came up with a quality finish - that's one of his strengths, running into the box and finding that corner. I feel it can be a turning point and I hope everyone at Everton can see what he can bring to the team."
