Thiago Silva admits he’s at a loss to explain Chelsea's stuttering form.
The Blues 3-1 loss to Manchester City on Sunday dropped them to eighth in the Premier League table.
It was a fifth league loss of the season, with pressure growing on boss Frank Lampard after taking just four points from a possible 18.
The likes of Timo Werner and Kai Havertz are currently struggling to show anything like their best form, while suggestions of a title push have dissipated.
Roy Keane, speaking on Sky Sports as a pundit on Sunday, declared: "Frank will be concerned for what he saw today."
But the Brazil captain says he can't understand what's gone wrong recently, after they struggled to get to grips with a City side who could, and probably should, have won by a bigger margin.
The veteran defender told RMC Sport: "No, I don't understand what's wrong.
“If I understand before, I think I could have given some advice, but that's how it is, it's football, it's the Premier League, one of the toughest championships around the world.
"You have to be careful, work harder, be stronger as a team, but I think the team is good, the second half was much better than the first in my opinion.
"We tried to play a little more, we managed to play. I think we were superior in possession of the ball in the second half, sometimes it does not work as we want, as we have prepared, but, that's how it is football.
“We must prepare for the next match when it arrives."
The former Paris Saint-Germain and AC Milan centre-back also admitted to BBC Sport that the first-half performance of Pep Guardiola’s men - which led to Lampard conceding his side were outclassed - was a reminder of the standards the Blues need to reach.
“It was painful in the first half in football terms because their level of play shows where we need to aspire to.
“In the second half I saw a reaction but the work needs to be done."
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