Kai Havertz put in another underwhelming Premier League display for Chelsea on Saturday - the first player to be substituted by Frank Lampard despite the hunt for an equaliser away at Everton.
Despite that uncharacteristic error from Mendy, much of the focus afterwards was on the club's £70 million ($97m) signing Havertz, who again failed to create for his team while playing out on the right wing.
Lampard had talked up his 21-year-old capture from Bayer Leverkusen ahead of kick-off, stating that he would one day become one of the best players on the planet.
"He has all the attributes, all the personality, all the attitude and he’s going to be an absolutely top-class player for me, in the Premier League and in the world," Lampard said last week.
But despite Chelsea’s total dominance in possession, Havertz only managed one shot and one key pass in his 68 minutes on the pitch.
He was playing in place of an injured Hakim Ziyech, who has produced a number of man-of-the-match displays since joining from Ajax.
It hasn't quite happened in the same way for Havertz, who was playing out wide with Callum Hudson-Odoi also injured and Christian Pulisic left out for precautionary reasons.
"He had to be left out," Lampard said of Pulisic, who was expected to be in the squad. "He was uncomfortable in training this week and yesterday. He can’t play 90 minutes or start a game in the Premier League.
"Did we miss the wide players today? Yes, we did, because they are big players for us."
The versatile Havertz proved he could play out wide during his time in the Bundesliga but all his best displays at Chelsea have come through the middle.
Lampard initially began with Havertz in the No.10 role but it was one factor in unbalancing the team. Ultimately, he looked most at ease in a No.8 role after Chelsea’s succesful switch to the 4-3-3 formation.
Havertz had warned he would need time to adapt to English football when he was unveiled to the world's media. On media duties ahead of kick-off, he reminded the world that how serious it is to catch Covid-19 having suffered from it three weeks ago.
"When you do nothing for two-and-half weeks and then you start training again, you feel like you have never played football before. For me it took two or three weeks to get back to 100 per cent," Havertz told BBC Sport's 'Football Focus'.
"Now I have started three games and I'm feeling good. It takes a lot of time and it took around one-and-a-half months for me to get back but now I think I am very fit again and can start to attack again."
With that in mind, it is harsh to draw any long-term negative conclusions about the signing of Havertz, particularly after seeing all the club's new signings struggle against Carlo Ancelotti's side.
Thiago Silva and Ben Chilwell looked defensively weak for much of the game, with the England full-back almost giving away a penalty through poor defending, only to be saved by VAR.
Timo Werner had an impressive start to life at Stamford Bridge after joining from RB Leipzig in a £47.5m ($59m) move, but was unimpressive and is now on a run that has seen him draw a blank across eight games for club and country.
Havertz should not be scapegoated, with clear mitigating reasons for his current form. At the top level, the levels of scrutiny can often crush a player's confidence - as Chelsea have seen with their record signing Kepa Arrizabalaga.
Chelsea will ultimately need more from the Germany international but they need to also protect him.
He deserves more time to recover, adapt and shine again because, up to now, Lampard has not got the best out of him.