Raheem Sterling's lightning start to the season undoubtedly highlighted the immense extent to which he has improved in recent years, becoming a regular Manchester City match-winner almost as decisive as Sergio Aguero.

He struck his sixth Premier League goal of the season in Saturday's 3-1 win at Everton, and although his performance was otherwise erratic, the England international's persistence showed just how far he has come.

It was by no means vintage City on display at Goodison Park, as Everton were unfortunate to not come away with at least a point.

Pep Guardiola's myriad of defensive issues again reared their head, with Everton bullying them aerially on numerous occasions – Yerry Mina proving a colossal thorn in City's side with his prowess in the air.

Hindsight is 20-20, but even before Aymeric Laporte's serious knee injury, it was clear City needed greater depth in quality at the back, yet the failure to secure Harry Maguire did not lead to the arrival of anyone else.

With John Stones joining Laporte in the treatment room, Fernandinho has filled in capably at the back for the past three matches, but at Goodison he looked every inch the makeshift option he is – a feeble clearance and attempted tackle leading to Everton's equaliser.

Beside him Nicolas Otamendi was no more convincing, the Argentina defender routinely struggling aerially against Mina at set-pieces.

Aside from Gabriel Jesus' header after Kevin De Bruyne's outrageous cross, City were similarly unimpressive in the opposing penalty area for long periods of the match as well.

Sterling spurned a glorious chance on the hour, inexplicably missing the target when one-on-one with Jordan Pickford, a let-off that suggested Everton might just hang on for a point.

Mahrez had other ideas, however.

The Algerian has struggled for consistency since joining City in his big-money move last year, but when expertly bending a 30-yard free-kick into the bottom-left corner with 19 minutes to go, he was netting in a third successive start across all competitions.

There was more to Mahrez's performance than just that goal, however, the winger toying with Lucas Digne relentlessly – and his solo run leading to De Bruyne's pass for the opener.

All five of the winger's shots were on target and he also laid on five opportunities for team-mates, a figure bettered by no one else on the pitch.

Mahrez then troubled Everton for City's final goal, his cross finding its way through to Sterling after and the former Liverpool talent slammed an effort in off the crossbar, holding his nerve when he might have failed in the past on an otherwise frustrating day for him.

A consistent Mahrez added to attacking options including an unflappable Sterling should make City unstoppable, yet as impressive as the champions' attitude was on Saturday, there remain the lingering defensive doubts that could ultimately cost them the title.