Chelsea have suffered a disappointing start to the season and many fans have been pointing the finger at two players they believe are to blame for their struggles.

Almost from the moment he joined Chelsea from Marseille in the summer of 2012 – a bargain at just £7m – Cesar Azpilicueta has been a symbol of dependability.

Managers came and went, but Azpilicueta’s name never left the team sheet. Why would it?

You’d be hard stretched to find a better poster boy for the phrase “model professional”, and whether playing at right-back, left-back, or as part of a back three, he was not only reliable in defence, but a dangerous weapon going forward. Any manager’s dream.

But this season cracks have started to show – and they’re not just hairline fractures.

Both of Sheffield United’s goals at the weekend came from moves down Chelsea’s right side, with Azpilicueta getting nutmegged by Enda Stevens in the build-up to Callum Robinson’s first, before he failed to prevent Stevens’ cross for the late equaliser, accidentally turned in by Kurt Zouma.

Azpilicueta was responsible for two of Manchester United’s four goals in the heavy defeat at Old Trafford on the opening weekend of the season and gave the ball away 22 times that day – more than any other Chelsea player.

On Saturday it was 20, and it’s now becoming hard to argue the Chelsea captain isn’t becoming something of a weak spot in the line-up – one which needs its senior players to stand up and be counted in order to allow Frank Lampard to feel confident in continuing to put his trust in youth.

Other teams have clearly noticed Azpilicueta’s vulnerability. Manchester United, Norwich and Sheffield United all launched significantly more attacks down the Chelsea right than the rest of the pitch.

It was most pronounced at Norwich, where 58% of moves targeted the Spaniard’s side, compared with 14% down the middle and 28 per cent down the right. Manchester United sent 49% of attacks towards Azpilicueta and Sheffield United 50%.

Azpilicueta’s rap sheet is growing and the question must be asked: how long can this continue before he drops out of the team?

He was caught for two of the goals away to Manchester United; deserves some blame for those conceded to Liverpool; Leicester City’s equaliser arrived from his side of the pitch, and he was far from impressive away to Norwich City.

That pattern has become impossible to ignore but other habits are beginning to become increasingly ingrained, too.

It’s hard to say whether this is a genuine decline or simply a blip in form. Azpilicueta has only just turned 30, but he has played more minutes than any other outfield player in the league since he arrived in England seven years ago. That kind of workload can take its toll.

In his defence, he has been playing in a much more inexperienced back four this season, alongside players he has not spent much time with. Antonio Rudiger has been out with a knee injury and David Luiz has been sold to Arsenal, while N’Golo Kante’s limited availability has left the entire defence more vulnerable.

New units can take a while to gel, and it’s far too early to write Azpilicueta off completely on the back of a few iffy performances.

Having let Davide Zappacosta go on loan to Roma, the most likely challenger to Azpilicueta’s position is Reece James – except the 19-year-old injured ankle ligaments during the Toulon Tournament and is still a couple of weeks from returning following surgery.

Fikayo Tomori, who replaced Andreas Christensen at centre back on Saturday, can also operate there – but it is not an area of the pitch where Chelsea are blessed with depth.

Another Chelsea player under fire as well is Kurt Zouma.

Just weeks after conceding the penalty for Manchester United’s opening goal in a 4-0 thrashing, the Frenchman found himself on the wrong end of the headlines again on Saturday.

As Chelsea appeared to close in on their first home league victory of the season against Sheffield United, Zouma contrived to turn a cross into his own net and cost his side two precious points.

Aside from his costly own goal, the Frenchman had a generally miserable game for the Blues, failing to make a single tackle, interception or blocked shot in the entire game.

Zouma got an earful from Chelsea fans for his horrid afternoon at Old Trafford and after seeing the 24-year-old’s performance at Stamford Bridge, he could see himself axed from the Chelsea lineup.

Zouma looks all but of the squad as a fully fit Rudiger will be available after the international break and will obviously replace the Frenchman.

Even without Zouma having horror shows, Rudiger is way better and it was inevitable he (Zouma) was going to be dropped. But with all of his terrible performances, Lampard will be a happy man to welcome Rudiger back in action.

Conclusion

Lampard’s Chelsea have looked refreshing going forward but the disorderliness at the back has been a major cause for worry.

Chelsea have only won one out of four games and it gets more worrying when you consider that two out of those four games were against newly-promoted sides and still they had to grind out results.

Lampard must now address the situation and be ruthless in dropping these players to the bench or continue to watch his side give away points.