Everton was dealt a big blow ahead of it first Premier League match of the season with Leighton Baines' exclusion from the starting squad due to an ankle injury suffered during training.
The English international was left off the team sheet selected to face Watford after injuring the same ankle he had surgery on in May.
A timetable for his return was not disclosed, but the prognosis doesn't appear promising as manager Roberto Martinez expressed his disappointment at losing such an important player before the season starts.
"With Leighton, it was a very, very unfortunate block in training, where the ball hit his ankle that he had a little bit of trouble with in the later stages of last season," Martinez said.
"It's really sad and disappointing because Leighton came back probably stronger than ever and this pre-season he showed fantastic signs. So, to lose him in the week that you're preparing to start the season is very disappointing.
Martinez went on to hint that the ailment could be a recurrence of the injury that required surgery, likely meaning Baines could be forced to miss multiple months, with the possibility of undergoing another procedure.
"We're just hoping we can get him back quicker than we fear because the injury looks very similar to what he had before."
Baines had been bothered by the initial injury for some time before opting to undergo season-ending surgery in May. He was ruled out of Everton's preseason tour of Singapore in July, but finally made his return to the squad during a friendly at the end of the month.
