Chelsea manager Roberto Di Matteo has already had to deal with several players leaving this summer at the end of their contracts but with key duo Frank Lampard and Ashley Cole entering the final year of their respective deals, are they still needed around Stamford Bridge and just what would they do if they both left?

Having already seen the end of an era with Didier Drogba departing to Chinese outfit Shanghai Shenhua this summer and with Salomon Kalou following him out of the door to Lille, these losses were eased by the arrivals of Eden Hazard and Oscar and there's a real sense that while the side is certainly in transition, that an exciting new cycle is beginning.

Cole and Lampard represent two of the oldest and last bastions of the Mourinho reign left in the squad, along with the likes of John Terry and Petr Cech, yet both haven't signed new deals at the club and Chelsea's policy, very similar to the one which saw Robert Pires leave Arsenal, means that they only offer players over the age of 30 one-year extensions.

Former manager Andre Villas-Boas was heavily criticised for benching Lampard on occasion, although not as much as his media pals would have you believe, yet Di Matteo has seen fit to leave the England international out of recent big-game clashes against Arsenal and Manchester United, with the more energetic presence of Ramires often preferred in the centre alongside the more steady John  Obi Mikel.

With rumours of a move to MLS club LA Galaxy refusing to go away and the dawning realisation the the triumvirate of Hazard, Oscar and the sublime Juan Mata have essentially made themselves undroppable with their form recently, then now may be the time for the 34-year-old to move on.

That is not to say of course that Lampard still has nothing to offer, for he's never been a player that's relied on pace, rather his instinctive ability to time his runs forward, but in a more reserved, deeper-lying role screening in front of the back four, he has become less effective at what he's best at, even if he should be applauded for adapting to a role many previously assumed was beyond him.

Spaniard Oriol Romeu arrived from Barcelona with a burgeoning reputation and thrived under Villas-Boas, but has yet to quite break through in the same way under Di Matteo, but with Lucas Piazon also waiting in the wings, there's plenty of competition for places at a club that's never been shy of investing owner Roman Abramovich's billions in the transfer market.

You suspect that Lampard still has a role to play, albeit more of a squad one, but whether he'll want to see his career wind down at a club which he is so revered and has played such a large part in over the past decade remains to be seen. There's an expiry date on his usefulness, though, as cruel as that sounds and the niggling injuries are creeping in more regularly than they used to and pride could come into play. His goals are always a crucial outlet in terms of the whole team's overall contribution and his record bordering on the ridiculously good, but there's a sense that this Chelsea side is in good hands now and may be in danger of moving on without him.

When it comes to 31-year-old left-back Cole, though, the England regular certainly still has a big role to play over the course of the next few years, even if his powers may be slightly on the wane and with an heir apparent already involved in the side in Ryan Bertrand.

Di Matteo spoke last week of his willingness to sort out Cole's contract, stating: "He's a fit boy. He can play every game, so he still has many years in front of him. "My point is that I would like him to stay here and be here with us" and he's still a guaranteed starter at the moment, so to dither of the length of the deal would seem needlessly cautious, bordering on careless.

The one thing which helped Chelsea on their way to the Champions League and FA Cup last season was the consistency of the back four; they all know their roles in the side, what duties they are there to carry out and that they have the confidence of the man at the helm and this helped them as a unit and they became extremely difficult to break down and Cole was a large part of that.

His form at Euro 2012 was average, with both Mathieu Debuchy and Andriy Yarmolenko getting the better of him while Victor Moses gave him a good going over away at Wigan at the start of the campaign and two of Manchester United's goals at the weekend came directly from his poor positioning. He clearly needs to adapt to his increasing lack of pace, but the one thing going for Cole is that he's always been a good defender first and foremost and he should be up to the job.

The club are currently going through a period of change and there's been a radical overhaul of the club's formation and a slight tinkering with their style along the way. As such, Lampard is no longer the pivotal cog in the machine he once was and the side looks as if it can survive without him in its current guise, but to lose Cole at this stage would represent a gross error of judgement on the Chelsea's hierarchy's part and he needs to be assured of his importance or they run the risk of losing a very good, experienced player.

Which player do you think is most key to Chelsea's future - Cole or Lampard?

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