It's been a disappointing season for Everton, considering the vast amounts of talent the club boast within their ranks. Manager Roberto Martinez is seemingly constantly fighting off criticism as his gifted young side continue to leave themselves open in defence.

Despite leading the Toffees to the FA Cup semi-finals, as well as the same stage in the League Cup, there has been speculation over the future of Martinez on Merseyside.

Links away are something the Goodison Park outfit must be used to by now. While last summer was dominated by the John Stones saga, their relatively poor season this time around will surely see more of their big stars mentioned in the proverbial rumour mill.

Star striker Romelu Lukaku, scorer of 21 goals this term, has reportedly attracted the attention of the likes of Manchester United and Chelsea, while Ross Barkley's return to good form is unlikely to go unnoticed.

Naturally, Stones continues to be linked with some of the biggest European clubs around, despite having a tough time of it in recent weeks.

The recent announcement that Iranian businessman Farhad Moshiri is no doubt exciting, but the manner in which the club have continued to slip up this season will do little to keep the vultures from circling over their top talent.

So, with that in mind, here are FIVE key stars that could leave Everton this summer...

JOHN STONES

Everton must be applauded for the way in which they stood their ground and fought off Chelsea's interest in John Stones over the summer.

However, it's not all been plain sailing for the talented 22-year-old since. Often accused of over playing, the England international has found himself left out of the firing line after repeated criticism.

Though their refusal to depart with the former Barnsley trainee was admirable, it seems unlikely such a feat could be pulled off once again - especially considering the frustrating season at Goodison Park.

With Manchester City, and Pep Guardiola, reportedly circling, perhaps the Toffees will finally succumb to a huge money offer should it arrive.

KEVIN MIRALLAS

Aaron Lennon's renaissance (what an odd phrase that is) has seen the former Spurs winger establish himself as a key attacker alongside Barkley and Gerard Deulofeu recently.

In turn, that has seen Kevin Mirallas miss out on a first-team berth more often than not. The Belgian wide forward is clearly a talented player and increases the squad options hugely, though will surely not be content at merely a place on the bench.

He was linked with moves to the likes of AC Milan and West Ham over the course of the January transfer window though ultimately remained on Merseyside.

Still, the recent news regarding the investment due to arrive, an influx of players over the summer could see the 28-year old depart.

TIM HOWARD

Goalkeeper Tim Howard has been a wonderful servant to the club ever since he first arrived on loan from Manchester United 10 years ago this summer.

Still, Father Time takes no prisoners and the American custodian has lost the sheen of invincibility he has earned over his decade in England, as well as his performances at the 2014 World Cup.

All too often this season, the 36-year old has failed to command his defence and let things slip through his fingers, both literally and figuratively.

Roberto Martinez has seen fit to field Joel Robles in his place, with suggestions Howard could soon return to the MLS prevalent.

STEVEN PIENAAR

Another wonderful servant to the Toffees who could seen depart is Steven Pienaar. Out of contract in the summer, the 33-year old is all but certain to leave Goodison Park for the second time in his career.

Sadly, injuries have caught up with the South African legend and his last year or so has been dominated by them. With the club hopefully entering a new era thanks to their new investment, it is sadly time to say goodbye to the former Spurs winger.

A lucrative move to the Chinese Super League has been mooted upon the expiration of his deal on Merseyside, which could provide the ideal way to end his playing career.

ROMELU LUKAKU

While the previous two names in this gallery appear to be coming towards a natural end to their times with Everton, forward Romelu Lukaku is surely someone they would loathe to lose.

The 22-year old has come to the fore this season, notching 21 goals across all competitions and establishing himself as one of the top marksman in the country.

After a frustrating campaign last season, the former Chelsea man is beginning to show the sort of qualities that convinced the Toffees to splash £28m on him in the first place.

So much so in fact, that his former charges are understood to be considering a move to bring the Belgian back to Stamford Bridge. Such is the nature of his form, the Blues are reportedly not alone in their interest.

Manchester United and PSG have both been linked with the former West Brom loanee, in what is likely to be a hugely expensive move.

The way in which the club battled to keep John Stones last summer will no doubt encourage fans, though perhaps a mega money bid for their striker could turn heads at Goodison Park.