City, who have only been top for a total of six days all season, will have the chance to overtake Arsenal by beating next-to-last Burnley on Wednesday night after beating the Gunners 2-1 at the weekend.
O'Reilly set up the first goal for Rayan Cherki and later carried the ball 40 yards upfield, passing it to Jeremy Doku, who found Erling Haaland to score the winner on Sunday afternoon.
The young England star has been incredible for the side so far this season, leading the backline at just 21 years old.
Speaking after the game, Guardiola heaped praise on the starlet, who he believes should be handed an accolade for his efforts.
"What a season," Guardiola said of O'Reilly. "I don't know if he's the best player of the season, but the young one? It has to be delivered."
The likes of Steven Gerrard, Wayne Rooney, Cesc Fabregas, Ashley Young, James Milner, Eden Hazard, Bukayo Saka, Cole Palmer and many more have claimed such an award, which often predicts who the next big stars may be.
O'Reilly could certainly be one of them as fans look towards the future and City's next clash against Burnley, where the club could fire themselves to the top of the table.