Everton tweeted to say Oviedo had a suspected broken leg and such was the severity of the problem that his team-mates could not bare to look as he lay on the floor.
Blues boss Roberto Martinez said: "A real negative is the unfortunate incident and we end up with Bryan picking up a bad injury. We need to give him as much support as we can as he had a terrific season.
"I have been so impressed with his level in different positions. He's a really important player and we want to make sure everything goes well."
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