If Thomas Tuchel was not already 100% certain that Chelsea needed another center-back, he surely is now.
Chelsea lined up in a 4-2-3-1 formation at the start of Saturday's friendly against Arsenal in Orlando.
It was a disaster and Arsenal cruised to a 4-0 win.
Most of Chelsea's success under Tuchel, including their Champions League final victory in 2021, has come playing a 3-4-3 system.
But the Blues backline was decimated this summer by Andreas Christensen and Antonio Rudiger leaving on free transfers.
Kalidou Koulibaly has been brought in to help fill the void, while another center-back is top of Tuchel's wish-list.
But Koulibaly started Saturday's game on the bench as Tuchel opted to pair Trevoh Chalobah with Thiago Silva at the heart of his defense.
That defense was undone inside 15 minutes when a simple through-pass from Granit Xhaka found Gabriel Jesus, who chipped Edouard Mendy to make it 1-0.
Jesus deserves credit for the coolness of his finish but he was given a lot of assistance by those wearing blue.
At first glance, it looked like 37-year-old Silva was the obvious man to blame as he had failed to step up, thus playing Jesus onside.
But Silva had been left in an awful predicament by Chalobah, who had wondered towards the center of the field, vacating the space Jesus would go on to exploit.
Chalobah went AWOL again for Arsenal's second goal. He stepped out of position to close down Gabriel Martinelli, only to then back off, giving the Arsenal no.10 a clear five yards to turn and play the ball into the space Chalobah should have been occupying.
Silva moved across but could not get to Martin Odegaard in time to stop his clinical two-touch finish.
Tuchel was visibly furious on the sidelines and Chalobah was replaced by Malang Sarr during the half-time break.
Koulibaly came on in the 73rd minute to make his debut but Chelsea were already 3-0 down by this point after Bukayo Saka had added his name to the scoresheet.
Albert Sambi Lokonga added goal no.4 in stoppage time.