Pep Guardiola highlighted 18-year-old Rico Lewis' introduction as the turning point in Manchester City's 1-0 win at Chelsea on Thursday.

City were poor in the first half and somewhat fortunate to be level at the break, with Carney Chukwuemeka hitting the post for Chelsea.

But teenager Lewis, who had started each of City's two previous Premier League games, was introduced at half-time as Guardiola reverted to a back four.

Lewis slotted in at right-back but once again looked comfortable operating in central midfield areas, as Guardiola likes his full-backs to do, completing all of his 27 passes as City suddenly enjoyed much greater control – he was the only player with more than 16 pass attempts to record 100 percent accuracy.

Riyad Mahrez scored the winner in the 63rd minute after a wonderful pass from fellow substitute Jack Grealish, but it was Lewis whom Guardiola singled out as being decisive.

"In the last games, Rico has the ability to make his teammates play better," Guardiola told Sky Sports.

"So, there are players who play for themselves really well, but [Lewis] has the ability to make the whole team play better because every movement he does, he knows exactly what he has to do.

"He's playing the level he was playing against Chelsea in the EFL Cup, against Leeds, Liverpool. He changed the game."

For many, though, John Stones was the standout performer.

Not only was he typically assured on the ball – aside from one heavy first touch in the second half that invited pressure from Conor Gallagher – but he was solid defensively as well.

Stones tallied the most touches (102) and successful passes (85) of anyone on the pitch, meanwhile no one bettered his duels success (77.8 percent – minimum two duels contested) and only Thiago Silva (five) recorded more than his four clearances.

It was not so long ago that Stones' City future was looking uncertain, but Guardiola believes the England international is playing the best football of his time at the club.

"He played extraordinary in the World Cup," Guardiola said. "He can adapt perfectly in the build-up with three [at the back], [playing] wider. He has the calmness, the composure.

"He is playing at the best level, maybe for the first time in seven years since we arrived together.

"When he is stable here [pointing to his head], when his mood is good, he is a fantastic, fantastic player."

Thursday's result reduced the gap to leaders Arsenal to five points, which certainly does not look unassailable for a squad as deep as City's with 21 games left.

Guardiola was keen to give Arsenal their due credit, however, adamant the Gunners have even been impressive in the few games they failed to win.

"Well, it could have been seven points, or 10 or eight, but now the gap is five points," Guardiola said.

"We have to look at ourselves, but I have to admit, the way they are playing, Arsenal deserve to be there.

"It's not just about the points, the way they are playing. Even when they lost against [Manchester] United and drew with Newcastle, the quality and the level they are playing is so good."