Chelsea headed into the game on the back of a fairly poor run of form that includes losses to Leeds and Southampton.
Granted, they did beat West Ham over the weekend, but the Hammers were very unlucky not to walk away with a point.
As a result, the Blues were no doubt keen to bounce back on Tuesday and get their European journey off to a positive start.
Chelsea began the game the much brighter of the two sides and carved out a few chances early on.
The Blues’ front-three looked especially sharp, with Kai Havertz a lot more comfortable on the wing now Pierre-Emrick Aubameyang is playing up top. It was Aubameyang’s first appearance for his new club and he looked sharp from the get-go.
But for all Chelsea’s early dominance, it was Zagreb who took the lead via Mislav Orsic.
The forward was sent through on goal, outpacing Wesley Fofana before chipping Kepa.
After that goal, some fans have taken to social media to express their displeasure at their new signing: