The Costa Rica international was sidelined for eight months after an horrific double break of his left leg in January 2014 which ruled him out of last summer's World Cup, and the new injury means he will miss the CONCACAF Gold Cup this summer
Oviedo was due to make his comeback from a hamstring injury sustained in February in Thursday night's mini-Merseyside derby between Everton's under-21s and their Liverpool counterparts at Goodison Park.
"We had a real disappointing situation with Bryan Oviedo in training as he has fractured his fifth metatarsal (of his right foot) - which is incredibly bad luck," said manager Roberto Martinez.
"He was in a great moment of form to get back into the squad and finish the season playing but it was a very unfortunate action on his own and he is going to be out for the rest of the season.
"It is not his leg he had the break in, so there it is nothing to do with the mechanics involved but it means he will miss the Gold Cup for Costa Rica."
Ovideo had worked hard to regain full fitness after breaking his leg in an FA Cup fourth round tie at Stevenage, but despite making his comeback in September, his appearances were sporadic until he got a run of games from the turn of the year before pulling a hamstring in a Europa League tie against Young Boys.
"He has given us a lesson in terms of the mental strength he has," added Martinez.
"We were really gutted for him but he is the one leading the rehab and he is ready to count the days until he can come back.
"I would say mentally he is in a great place and is a great example to any footballer
He is just desperate to get back and be fully fit.
"It has been such an unfortunate period for him since the game against Stevenage - I am sure this is going to be the last unlucky chapter."
With Everton's form having picked up in recent weeks - winning five and drawing one of their last six matches - and the summer fast approaching, speculation has increased about the future of some of their players.
Forward Kevin Mirallas and James McCarthy appear to be the two most in-demand, and despite the pair expressing how content they are to stay at Goodison Park, Martinez expects the rumours to continue.
"They are performing extremely well and I think it is part of football when you perform well you attract speculation," he said.
"It is nice to see when players are happy and understand what it means to represent Everton but we all know football.
"We are not against attracting speculation or other clubs looking at our players because that is a good thing - the last thing you want is people not being interested in our assets.
"If anything we want to build on what we are doing at the end of the season and are looking to get through the next window with two or three additions."
One of those additions could be on-loan Tottenham winger Aaron Lennon, who has impressed since joining in January.
"Nothing has changed
We are going to leave that conversation until the end of the season," said the Toffees boss.
"It is about sitting down with Aaron, thanking him for his efforts and then it is a three-way conversation.
"We are very pleased with the manner Aaron has been able to play and clearly this loan has been a real success so far."
The future of one of Everton's academy graduates, Luke Garbutt, is also up in the air with the defender, who has made nine appearances this season, out of contract in the summer.
However, Martinez insists there is no concern over the left-back, who turns 22 next month.
"Luke is one of the prime examples of the focus we have in our academy players," said the Toffees boss.
"He has been terrific in terms of going through the programme we have put in place and we are looking forward to having Luke for many years to come.
"His situation needs to be solved and I am sure that is something we will look into in the summer.
"I don't see the contract situation as being a big issue
If Luke wants to stay at Everton we want him to stay at the club."
Source : PA
Source: PA