Manchester City forward Gabriel Jesus became the first player in Premier League history to have a goal ruled out by the video assistant referee (VAR) during his side's 5-0 victory over West Ham, which included a hat trick for Raheem Sterling.
The Brazil international gave the reigning champions the lead in the first half before Sterling tapped home Kevin De Bruyne's pass on 51 minutes.
City thought they had a third after a well-worked move involving Sterling and David Silva, which was finished off by Jesus -- only for referee Mike Dean to disallow the goal for offside following a consultation with VAR in the first season where the technology is present in the Premier League.
However, the third did eventually arrive on 75 minutes after Sterling was played in before delicately looping the ball over West Ham goalkeeper Lukasz Fabianski -- yet only after another check with VAR.
City were given a penalty on 83 minutes after Diop's foul on Riyad Mahrez and, despite Sterling being on course for a hat-trick, Sergio Aguero stepped up and saw his tame effort saved.
But, following encroachment by Declan Rice, Dean ordered a retake and the Argentina international made no mistake with his second effort. Sterling did get his hat-trick in stoppage time as he tapped home past Fabianksi.
City boss Pep Guardiola handed a debut to record signing Rodri, but Joao Cancelo was left on the bench, while new West Ham man Sebastien Haller started in attack for the hosts.
And Manuel Pellegrini's men began the game well, causing the visitors problems on the counterattack.
But they were behind on 25 minutes when Jesus squeezed the ball home from an acute angle following good work by Kyle Walker down the right flank.
City doubled their lead through Sterling and, after Jesus had seen his potential second chalked off by VAR, technology ensured the England international's second did count before he added a third late on, following Aguero's penalty.
The margin of victory sent City top above Liverpool, who had beaten Norwich 4-1 on Friday. West Ham travel to Brighton on Saturday in their next match before City host Tottenham later that same day.