Thomas Tuchel admitted Chelsea are struggling to protect their leads after the holders blew the chance to finish top of Champions League Group H in a dramatic 3-3 draw at Zenit Saint Petersburg on Wednesday.
Chelsea blow bid for first place as Zenit snatch dramatic draw
Zenit's Magomed Ozdoev celebrates after scoring against Chelsea
Tuchel's side had already qualified for the last 16 and were hoping to take first place to theoretically secure an easier draw in the knockout stages.
They were just seconds away from achieving their aim when Magomed Ozdoev fired home to leave Chelsea two points behind group winners Juventus.
Timo Werner had put Chelsea ahead after 84 seconds with his club's fastest ever Champions League goal.
Claudinho equalised and Sardar Azmoun handed Zenit the lead before half-time.
Romelu Lukaku, making his first start since suffering an ankle injury against Malmo in October, equalised with his first goal in 11 club games since the Chelsea striker netted against Zenit in September.
Werner looked to have won it with five minutes left, but Ozdoev's last-gasp goal added to Tuchel's mounting problems.
After Chelsea's damaging 3-2 defeat at West Ham knocked them off the top of the Premier League on Saturday, this was another setback for the Blues.
"My analysis is very clear: our behaviour changes when we have a lead and this is something we never did and we should never do," Tuchel said.
"Once we start managing results and changing our behaviour from what the score is, we get punished at the moment.
"Suddenly when we concede two goals we can show a reaction. But once we have the lead we give it away again. It happened to us at West Ham and it happened again today."
A long flight and temperatures well below zero made it a gruelling trip for a team already running on fumes and a return trip to Saint Petersburg for the Champions League final in May must seem a long way off for Tuchel's spluttering team at present.
Asked for the solution to Chelsea's dip in form, Tuchel said: "You have to play through pain and you have to raise your level of concentration and you have to overcome adversity.
"We need a higher level of sprints, a higher level of runs, a higher level of intensity and concentration. The basics need to be pushed onto a higher level while we are in the lead."
With N'Golo Kante still absent due to a knee injury, Jorginho unavailable because of a nagging back problem and Mateo Kovacic testing positive for the coronavirus this week, Chelsea's midfield was in tatters.
Saul Niguez has endured a difficult start following his loan switch from Atletico Madrid, but the Chelsea midfielder finally provided a positive contribution in the second minute.
Making a lung-bursting run from his unfamiliar left wing-back role, Saul's shot was pushed away for a corner by Zenit keeper Mikhail Kerzhakov.
From Ross Barkley's resulting set-piece, Andreas Christensen flicked on to Werner and he had the simple task of poking home from virtually on the goal-line.
So often this season, Chelsea have taken the lead without killing the game off and once again they were caught out in the 38th minute.
After Chelsea failed to clear their lines, Douglas Santos's cross found the visitors' defence flat-footed and Claudinho took full advantage with a glancing header past Kepa Arrizabalaga.
Three minutes later, Barkley surrendered possession too easily in midfield and Malcom's pass split the Chelsea defence, with Azmoun beating the flimsy offside trap and rounding Kepa before slotting into the empty net.
Lukaku grabbed Chelsea's equaliser in the 62nd minute, converting Werner's pass from close range.
Chelsea kept plugging away and looked to have won it in the 85th minute when Werner took Christian Pulisic's pass and drilled a low finish past Kerzhakov from 12 yards.
But there was a sting in the tale as Ozdoev lashed home from the edge of the area four minutes into stoppage time.
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