Everton manager Roberto Martinez has ruled out the prospect of selling star midfielder Ross Barkley to Manchester City in the January transfer window.According to Rob Shepherd of the Mail Online, the Toffees were considering cashing in on the 21-year-old England international for a figure between 45 million and 60 million. The piece claims that City see Barkley as a player who could give the champions added impetus in whats shaping up to be a fascinating title race with Chelsea.But as noted by Tony Barrett of The Times, Martinez has rubbished rumours of a move ahead Evertons upcoming Premier League clash with City:Paul Joyce of the Expresselaborated on what the Catalan boss had to say about the situation:As you can imagine this January window for us is vital for recapturing our best moment of form and start building momentum.Our best performers, if they get a lot of attraction, they will not be going in January.We will always be buyers. We really enjoy watching Ross. He is someone with real passion for the game. Youd always pay a good entrance fee to watch him.Barkleylike a host of Everton playershas struggled to hit the heights of last season during the current campaign. The youngster has been asked to play myriad different roles by his manager. That shifting around and injury problems have coalesced into a frustrating campaign for the Wavertree-born midfielder.Peter McPartland of The Blue Room thinks that while playing the youngster in different positions will eventually be good for his development, he needs a bit of stability to recapture his best form:There have been glimpses of Barkley's indisputable potential this season, though. His stunning goal against Queens Park Rangers was arguably the highlight of his campaign, and England coach Gary Neville was especially impressed by that strike, per Squawka Football:Its easy to see why City are potentially keen on Barkley. The club have a longstanding core of exceptional players, but a host of those men are approaching 30 years of age. With that in mind, its vital for Manuel Pellegrini to add some youthful endeavour to his team. Despite reports to the contrary, however, it doesnt look like Barkley will be that player quite yet.Everton can't afford to sell him, anyway. The Toffees are currently on a run of four straight defeats, and after securing a record points tally last season, Evertonians will be taking nervous looks over their shoulders in the coming weeks if things don't improve, as the Merseysiders are just four points clear of the relegation zone.One surefire way of surging up the table will be to find a way to get Barkley playing the way he did last season. Martinez needs to find a regular spot for the midfielder to enable him to establish some kind of consistency, and then we'll surely see a lot more of those patented surges forward with the ball.With City set to visit Goodison Park in Week 21 of the Premier League season, you wouldn't put it past this brash young talent to turn in a stellar display. Click here to read full news..