The summer signings from Bayer Leverkusen and Ajax have endured difficult starts to life in England, with Ziyech in particular struggling to get up to speed following the injury he picked up in pre-season against Brighton.
Havertz has demonstrated flashes of the talent which persuaded Frank Lampard to make him the joint most expensive signing in the club’s history, scoring a hat-trick in an EFL Cup thrashing of Barnsley, while he also opened his Premier League account in last weekend’s 3-3 draw against Southampton.
The 21-year-old was, however, guilty of conceding possession in a dangerous area and presented Danny Ings with the opportunity to bring the visitors back into what had been a one-sided contest.
Cahill has, similarly, been unimpressed with Ziyech’s early contributions and believes the Moroco international has been guilty of overindulgence during his two substitute outings so far.
Asked about Chelsea’s suspect defensive record, Cahill told Football Focus: ‘These are individual errors, it’s not the tactics. It’s a mentality, it’s individuals not focusing for 95 minutes.
‘On top of that you see the goals they concede. You see Havertz, he’s trying to do a trick, trying to nutmeg someone and he loses it. Ings is on the front foot, they’re ready, waiting and pounces.
‘There’s non-negotiables and they are don’t try and nutmeg someone on the edge of your own area, the other non-negotiable is stop dribbling and taking on 10 players.’