Covid cases wiping out their attacking threat, a defence leaking goals and Saul Niguez slated by fans... How the problems are mounting for boss Tuchel after Chelsea's slump from first to third 

When Thomas Tuchel opened the first door on his advent calendar, Chelsea were looking forward to a very happy Christmas indeed.

Already sitting top of the Premier League table, they won 2-1 at Watford on December 1 to stay ahead of Manchester City and Liverpool.

It was far from their most convincing performance but these are precisely the type of games you need to grind out three points in to win titles.

Chelsea dropped two important points in the title race as they were held by Everton  

Tuchel's team gave the impression of being consistent but also with plenty more to come.

But as December has progressed, Chelsea have stumbled and that festive cheers has drained away.

They lost 3-2 at West Ham, recovered to beat Leeds United by the same scoreline but then dropped two more points against Everton.

City and Liverpool, meanwhile, have rolled remorselessly on and suddenly Chelsea find themselves third, some four points off the top.

Thursday night's 1-1 draw against a depleted Everton team ended with boos around Stamford Bridge and the frustration is understandable.

So what has gone wrong and how does Tuchel stop the rot and keep Chelsea in the title picture?

Covid and injuries take their toll

The Omicron variant has not spared Stamford Bridge. Romelu Lukaku, Timo Werner and Callum Hudson-Odoi all tested positive ahead of the Everton game and entered isolation.

Mateo Kovacic was already there after returning a positive last week and Ben Chilwell, already out with a knee injury, also has Covid.

Kai Havertz had to be left out the squad on Thursday as he awaited test results.

So the disruption to Tuchel's plans for the match was certainly a mitigating factor. Christian Pulisic ended up leading the attack with Mason Mount and Hakim Ziyech playing behind him.

But Chelsea are far from alone in being ravaged by Covid as we enter the hectic Christmas fixture list. They were at least able to field a team, unlike quite a few in the Premier League.

Everton were without at least eight players through illness and injury, meaning 20-year-old debutant Ellis Simms played up front. Their goalscorer, Jarrad Branthwaite, 19, was making only his fifth league appearance.

At a time when serious consideration is being given to shutting the Premier League down over Christmas with barely a club untouched by the virus, Chelsea have their Covid issues but are far from the worst-affected.

'I am concerned we have too many players out, today six or seven players,' said Tuchel afterwards. 'I think this, in the moment, is the problem, one of the key problems.'

True, but Chelsea should have a depth of quality in their squad to mean this isn't an excuse.

Wasteful finishing

80 per cent possession and 23 shots against Everton tells its own story of dominance. How did Chelsea only manage to score the one goal?

It has become a familiar story. They had 19 shots in the defeat by West Ham but were ultimately let down by their own sloppiness.

Jordan Pickford was in inspired form on Thursday but you'd have thought the combined talents of Pulisic, Ziyech and Mount would have produced more than one goal.

In Pulisic's defence, his season has been disrupted by an ankle injury and he's started just four matches as a result of this and the intense competition for places. He isn't fully match sharp.

Not that Lukaku would necessary have been a lot better. The Belgian striker, who cost Chelsea £97million in the summer, has scored only once since September 14.

His encouraging start to the season quickly faded and Covid will now see him sidelined for Sunday's trip to Wolves, the Carabao Cup quarter-final with Brentford and possibly the Boxing Day trip to Aston Villa.

Werner, meanwhile, has scored just one Premier League goal all season, the same return as Hudson-Odoi. All of Chelsea's forwards are not firing as Tuchel would like and it's a big issue when chances are being created and not taken.

Just as well Mount is in good form - this was his fourth goal in his last four league outings - but he's one of few playing well.

Defence starting to leak goals

Chelsea's back line was largely impregnable during the opening weeks of the season, with Tuchel taking as much pride in clean sheets as the goals they were racking up.

Antonio Rudiger was - and still is - enjoying an outstanding season, Thiago Silva still looks a spring chicken at 37, while Cesar Azpilicueta and Andreas Christensen also find the three-man defence to their liking.

But of late, this once-solid unit has started to leak goals too easily. It's 10 in five matches in the Premier League and Champions League this month.

By contrast, they let in just two in five games during October and the same in November.

In previous games, if the forwards didn't take all their chances, it often didn't matter because the defence was so solid or keeper Edouard Mendy would make key saves.

Now they can't be so certain. They need to rediscover the defensive cohesion that earlier in the season was the bedrock of their winning form.

Don't call on Saul

It just hasn't happened for Saul Niguez since he arrived on loan from Atletico Madrid and Thursday night's appearance off the bench may well have been his worst yet.

The Spanish midfielder was slated by fans on social media with some calling on Chelsea to cut short his deal and return him to Madrid.

Tuchel always seems to play Saul in a different position, which doesn't help, but it was a sign of the moving parts in midfield with N'Golo Kante only just returning and Kovacic out.

The sooner Kante returns to give Chelsea more control, the better. The fact Ross Barkley, a forgotten man at Stamford Bridge until an unexpected revival this season, had to come on for Ruben Loftus-Cheek also wasn't the best sign.

It will be better when Chelsea are restored to their full midfield strength but you wonder how much more Saul will play for the club.