"Still hes loses simple balls, like the Tottenham game when he made an awesome assist in the first few minutes but then lost a lot of balls".
Despite the emphatic nature of City's victory, Guardiola admitted his side's defending can improve after Southampton squandered chances to narrow the deficit.
It took a further six minutes for City to double the lead, Bernardo Silva setting free Sterling on the right and the England forward selflessly squaring for Aguero to hammer in from close range.
Aguero set up Sterling for the fifth, from a wide angle, in the 66th minute and Sane completed the rout in the dying seconds from 18 yards after Sterling's third assist.
Morata has now scored four in his last four Premier League games after just two goals in his previous 20 domestic matches, and his return to form could be the final ingredient Sarri's side need to mount a serious title challenge.
"The difference is in his head", said Guardiola. "But still he is so young to consider among the world's best players", said the Catalan.
The Spaniard continued: "The first season, he was scared, he was looking, who is the guy I am going to pass the ball to? You don't expect an injury but now I am good, it is nice to be scoring".
"If he is stable and he focuses on what he has to do to become a better and better player, if he has this on his mind, he can reach whatever he wants".
Hughes said: "The disappointment for us is that if we were a little bit resolute, and better defensively collectively, not just the guys at the back, I thought we caused them problems going forwards".
Ever the perfectionist, Guardiola still saw enough to demand improvements.
- Ings's penalty for Southampton was their first goal in 505 minutes of Premier League football, and subsequently ended City's run of 630 minutes without conceding a goal in the competition.
"Opening period is always important in any game and we didn't really acquit ourselves well. Improving after winning is so much easier than improving after losing!"
"He is a top player but still is so young to be considered the world's best", said the City boss.