Chelsea’s soft underbelly was exposed again in defeat at Atalanta - they must toughen up or expect their four-game winless run to continue.
Any talk of challenging for the Premier League title can be dismissed if Enzo Maresca's young side doesn't start showing some steel. Their humbling defeat at Leeds was a wake-up call, but they showed little learning from that on Tuesday night.
Not for 44 games in the Champions League had Chelsea lost after scoring the opening goal, and it was the first time since 2005 that they were beaten away from home after leading at half-time.
Atalanta pressed and harried Chelsea, but this should not have come as a surprise. Not only is it how the Serie A club operate on home turf, but as a fellow Italian and friend of Atalanta boss Raffaele Palladino, Maresca would have known exactly what was coming.
Five changes from the weekend's draw against Bournemouth did not help. Some were forced through injury or rest, others were not. Rotation is key with such a heavy schedule, but at the moment, it is working against rather than for them, particularly at the back.
Maresca defended the changes. "If you see the five changes that we did compared to Bournemouth, it's different," he said. "But we had eight, nine players that are the same as against Barcelona, Arsenal, Tottenham and Wolves. The ones that they play tonight are the ones that they are playing in almost all the games."
Their rhythm in defence was broken further when Trevoh Chalobah was substituted at half-time for Wesley Fofana, who was later forced off with injury. "It was a little bit planned because Trev is playing every game," said Maresca, but it was also a risk-averse decision. "Also, because Trev had a yellow card."
There were errors for both goals. Gianluca Scamacca peeled away too easily for his header, while Marc Cucurella, concerned by the overlapping run of Davide Zappacosta, backed off while waiting for support from Benoit Badiashile, which invited Charles De Ketelaere to shoot and score.
"Mostly if the full-back comes [out], I try to give [the ball] to the wingback," said the goalscorer. "They kept dropping back so I shot." Chelsea made a rod for their own back.
Chelsea's brightest player was 19-year-old Josh Acheampong, who made a series of superb tackles and blocks to keep the Blues in the game. Maresca said he regretted not playing the teenager against Leeds, but would have been delighted with his showing in Italy. Acheampong has the required grit.
Chelsea's drop off has been concerning since title contender talk began following their spirited draw against Arsenal and the dismantling of Barcelona.
They were too easily beaten by Leeds, who had taken lessons from their previous match against Manchester City and used them to full effect. Bournemouth too, themselves struggling for form, never looked to be in danger of losing to Chelsea.
Maresca's side has started to look like what they should be: a naive, inexperienced group of talented youngsters. Their game management and mentality has to improve.
Some may also point to the Club World Cup exertions over the summer starting to take their toll, giving the Blues an extended season and a short pre-season. Maresca said: "After the first goal, we lost a little bit of control of the game. Also, we are playing every two days. We look like we struggle a little bit."
Yet their hopes of avoiding a Champions League play-off game and a further fixture pile-up have taken a huge hit with the defeat in Italy. "If we want to try to finish top eight, we need to win both," said Maresca of their final matches against Pafos and Napoli.
The next target for this team is consistency, in both performances and results. The Premier League and Champions League tables are incredibly tight, and every point counts. They have not learned how to grind out a result.
It does not get easier with a visit of Everton this weekend. They have won four of their last five Premier League games, vastly improved under David Moyes and will not have a midweek game to contend with.
There will be some returns and likely more rotation, but it is the wrong time of year to start having a blip. Chelsea need to rediscover their winning touch and soon. It starts with growing up.