Roberto Martinez's team were leading 1-0 when Oviedo collapsed in agony after a first half challenge on Stevenage's Simon Heslop that appeared to badly damage his ankle.

The Costa Rica international needed lengthy treatment from medical staff before eventually being stretchered off.

Everton team-mates Leighton Baines and Kevin Mirallas were visibly distressed after going over to check on Oviedo.

Leon Osman came on to replace the 23-year-old, who was immediately taken to hospital in an ambulance.

Oviedo's Everton team-mate Darron Gibson, currently sidelined by a knee injury, tweeted: "Really feel for Bryan there, looked like a bad one!"

If Oviedo's injury is as bad as feared, he will face a race against time to recover for the World Cup in Brazil, where Costa Rica face England, Italy and Uruguay in the group stage.