Chelsea beat Arsenal 3-2 in a thrilling Premier League encounter at Stamford Bridge on Saturday evening.
The Blues raced into a two-goal lead thanks to goals from Pedro and Alvaro Morata.
But Arsenal responded swiftly through Henrikh Mkhitaryan and Alex Iwobi to level the scores before half-time.
The game was on a knife-edge until Chelsea substitutes Eden Hazard and Mateo Kovacic entered the fray.
Maurizio Sarri's side put pressure on the Arsenal defence and Marcos Alonso eventually made them pay with a winner in the 81st minute.
Signed on loan from Real Madrid, Kovacic produced an excellent cameo performance on his Premier League debut.
As good as Kovacic was, footage has emerged which shows that he was lucky not to be booked in the build-up to Chelsea's winner.
The 24-year-old won a foul for a clear dive just 35 seconds before Alonso tucked in the winner.
Martin Atkinson's incorrect decision cost the Gunners dearly.
What's worse is that Arsenal would've been on the counter-attack if the foul wasn't given against Aaron Ramsey.
Kovacic was pleased with his Chelsea debut and is surely in contention to start against Newcastle next weekend.
He told Sport Klub: "First of all I’m happy about the win and that’s the most important thing, it’s good that the team is playing well so it’s easy to adapt.
"But I’m still out of rhythm since I’ve just joined the squad, but I’m working well and I’m improving and that’s what matters."
It's been an excellent start in west London for Sarri.
Meanwhile, Unai Emery will hope to pick up his first points of the season when Arsenal host West Ham on Saturday afternoon.
The former PSG coach insisted he is calm but urged his team to improve.
"We need to improve, and to be competitive each match, and know, or learn in the match," Emery told reporters.
"I am calm when I look at my team creating chances. But we need to continue working."