Chelsea have made an indifferent start to the defence of their Premier League title.The Blues are currently fourth in the table, already nine points behind leaders Manchester City through 10 matches.It’s too early to rule them out just yet but Antonio Conte may not be given a great deal of time to fix Chelsea’s problems if the situation doesn’t improve immediately.According to The Times, Roman Abramovich will consider firing the Italian if Chelsea lose to Manchester United on Sunday.Conte probably didn’t need the added pressure as he prepares to take on Jose Mourinho’s side, who have lost just once all season.But that’s what happens when you go down 3-0 against Roma in the Champions League, with Chelsea producing an uninspired display in Italy.Chelsea fans will have their own explanations for the club’s struggles but Alan Shearer has identified three of them.

Shearer explains Chelsea's problems

The Premier League’s all-time leading goalscorer believes their problems are a result of being in the Champions League, Diego Costa’s move to Atletico Madrid and the sale of Nemanja Matic to Manchester United.

“Several reasons,” Shearer told Coral. “One is that they’re now back in Champions League football. To win the league last year they didn’t have any of that so while all the teams were travelling half way across the world, Chelsea were resting.

“The second is Costa.

“And Matic. To let Matic go was a huge surprise. A big mistake in my opinion.

“We know the Costa situation but if you put all of those reasons together, that’s why their performances have been so indifferent.”

Shearer: Matic sale was a huge mistake

On Matic’s £40 million move to Old Trafford, Shearer added: “Whoever made the decision [to let Matic sign for Manchester United], it’s a huge mistake.

“To let him go was a gamble, to let him go to one of your rivals and to Manchester United - and he’s been one of their best players this year - was a huge mistake.”

Even Chelsea fans will have a hard time arguing with Shearer.

Matic has immediately developed into an integral part of Man United’s midfield, the Serbian starring in Tuesday’s 2-0 win over Benfica.

And his absence hasn’t gone unnoticed by Chelsea players, with Thibaut Courtois admitting this week that Matic is missed at Stamford Bridge.

“We know Nemanja’s qualities, he is someone who last year gave us the balance as well," Courtois said, per the Evening Standard.

"He decided to go to another team, so we won’t live in the past.”