Things can change very quickly in the world of football — something Chelsea boss Thomas Tuchel will happily testify.

At the start of the month, he watched the Blues defeat Watford 2-1 at Vicarage Road to stay top of the Premier League.

But in the five games that have followed in all competitions, the German has overseen only one victory and his troops now trail table-toppers Manchester City by six points. 

Ahead of tonight’s Carabao Cup quarter-final clash at Brentford, we explore whether the previously untouchable tactician may now be looking nervously over his shoulder. 

Hard to believe

At most clubs, a handful of dropped points would not give a manager too much cause for concern — especially when their previous achievements read as impressively as Tuchel’s.

Arriving at Stamford Bridge just under a year ago, the 48-year-old coach inherited a side languishing in mid-table and totally transformed them.

Pairing fourth place in the Premier League with a remarkable Champions League triumph, the man in the dugout received plaudits from all corners.

Without doubt, Tuchel outperformed predecessor Frank Lampard, although perhaps not by as much as the achievements alone would suggest.

Blues legend Lampard, 43, was axed in January after a run of torrid results — but only one month earlier, his side had also sat top of the league.

That is precisely why Tuchel cannot afford to rest easy. 

As we all know, the Chelsea board never let sentiment or past achievements skew their judgement when it comes to business decisions. 

Mounting injuries

Identifying exactly what has gone wrong for Tuchel’s troops in recent weeks is not straightforward but there is one factor that simply cannot be overlooked.

The Blues have been plagued with absentees, going without several key players through a mixture of coronavirus outbreaks and injuries.

Even though the likes of N’Golo Kante and Mateo Kovacic have recently returned from spells on the sidelines, problems remain in forward areas with Romelu Lukaku, Timo Werner and Callum Hudson-Odoi all missing last Sunday's goalless draw at Wolves. 

The attacking trio tested positive for coronavirus — a situation that led Tuchel to publicly question the continuation of top-flight fixtures in the midst of rising case numbers.

He said: "We have dinner together and then we have another positive test with Jorginho. People are worried because they are on the same bus and at the same dinner. 

"Obviously, it was not enough to postpone the match so we had to play. But our situation is not safe. Hopefully it does stop and we hope for the best."

Despite his concerns, the Premier League opted to continue playing over the festive period at an emergency meeting on Monday.

More to it

Every squad copes with absences throughout the season and it is fair to say Chelsea’s back-up stars have not seized their opportunities.

Taking the team's last four Premier League games in isolation, they are averaging 0.86 fewer goals per 90 minutes than in their previous 14 encounters.

Bizarrely, however, they have had more of the ball than normal in those recent contests — it has been a lack of cutting edge that has proved costly.

Chelsea's forward passing percentage is significantly down and profligacy has also been an issue, as illustrated by an increase in their big opportunities missed metric.

Simply put, Chelsea are still controlling games but are finding it difficult to translate domination into points.

This has rarely been more evident than in the recent 1-1 draw with a threadbare Everton, where Tuchel’s side had 23 shots and a staggering 81% possession but could only breach the Toffees’ backline once.

Pressure rising

With seven points dropped in their last four games, Chelsea's title hopes have taken a hammer blow. 

Although the season is not even at its halfway point, clawing back the gap to relentless City will be no easy task — and it could still widen further on current form.

Facing potential banana skins against Aston Villa and Brighton in their next two league encounters, the Blues then tackle a titanic January, hosting Jurgen Klopp’s Liverpool and Antonio Conte’s Tottenham either side of a trip to the Etihad.

Tuchel needs his key men back quickly to stand any chance of negotiating that run successfully.

Looking further ahead, an arguably inconvenient Club World Cup trip awaits in February before a kind-looking Champions League last-16 draw with Lille.

It is quite feasible the season will soon turn into another cup campaign for Chelsea, which is unlikely to amuse the Bridge powerbrokers having backed their manager significantly during the summer transfer window.

Perhaps beating Brentford tonight is more important than it looks for Tuchel.