With Manchester City missing Rodri for the first time since his serious knee injury, this victory against Watford, the Championship’s eighth-placed side, offers scant clues regarding how they may cope in the long term. For that, the trip to Newcastle on Saturday will offer more insight into Pep Guardiola’s plan, and which senior player the manager trusts to deputise for the 28-year-old in the pivotal midfield role. In this game Nico O’Reilly, 19, in a first competitive start, occupied the vaunted Spaniard’s No 6 berth, and although he will not do so against greater opposition, as an audition to make regular match-day squads this tidy display did him no harm. The City machine was in threshing mode inside five minutes via a ruthless Jérémy Doku finish. After Watford dithered at the back, James McAtee, at the left byline, spun and fed Jack Grealish. The No 10 angled the ball to the Belgian, who smoothly outmanoeuvred James Morris and beat Jonathan Bond, the visiting goalkeeper. In pre-season, Guardiola quipped about the 6ft 2in O’Reilly’s height, saying this made a change from City’s more diminutive academy products, Rico Lewis and Oscar Bobb. Rodri, too, is statuesque, and a simple O’Reilly touch to Lewis inside Watford was also reminiscent of the injured man with a cuteness that surprised the right-back. An O’Reilly snap-tackle of Imrân Louza that left the No 10 in a heap and set City on the attack will have pleased Guardiola, although less so an attempt to dribble that gave up possession, a cardinal sin in the eyes of the manager. Guardiola made nine changes from the feisty 2-2 here with Arsenal on Sunday. Kaden Braithwaite became the club’s third‑youngest debutant at 16 years and 229 days. He was barged aside by Kwadwo Baah on the way to scoring an apparent equaliser, before a foul was called by David Webb, the referee. A 50-50 call, this may not have been given outside City’s area, so the youngster was lucky and the Hornets the opposite. The hack on Phil Foden as he ran on to a Grealish pass was a certain infringement and the two stood over the free-kick before Foden slammed it into Watford’s wall from near the edge of the area. Ten minutes from the break, Nunes did far better. Lewis, drifting inside, pinged the ball to McAtee, who returned it. The defender tapped it to Nunes who, sensing the yellow shirts around him dawdling, moved the ball left and then beat Bond to his right from 20 yards out. Guardiola’s expertly drilled unit had their opposition where he likes them: on the wrong end of a deficit and having to face a relentless blue onslaught. This was the pattern of the opening half until Webb blew for time. But if the unmarked Vakoun Bayo had not spurned an easy header just before, the managers’ team talks would have been very different. Savinho, whose soft-shoe shuffle and turn inside created Erling Haaland’s opener against Arsenal, was given the second 45 minutes, as Doku was taken off. Link-play involving the Brazilian led to a corner but from it McAtee blasted a pass to Lewis, who miscontrolled, and Watford broke downfield. Nunes had to do fine work in sprinting back to help kill the threat. Lewis then weighted the ball perfectly for McAtee running into the visitors’ area but his touch was clumsy and Bond gathered. City were revving up. Two twisting Foden efforts claimed two corners. A Savinho laser rippled the side-netting. Down the left, Grealish probed and teased a rearguard as entrenched as the Gunners were during their second half here. To see Ruben Dias, Bernardo Silva and Mateo Kovacic warming up was no succour for Tom Cleverley’s men but the corner they claimed was. The ball begged to be smashed home when dropping enticingly on to Louza’s boot but his volley was wild. Seconds later City were again at Watford’s throats as Nunes and Lewis went close and Tom Ince cleared from Savinho off the line. This was all frantic. A concerned Guardiola nearly rued these near‑misses as Watford broke again and Baah narrowly missed from near Stefan Ortega’s goal. At the other end, Savinho went closer, hitting Bond’s right post, drawing “oohs” from an under-capacity crowd. O’Reilly’s night was over, Jacob Wright replacing him, as was Braithwaite’s a little after, Josko Gvardiol taking up his left-back berth. Grealish, from point-blank range, pummelled the ball into Bond’s chest. The wide man should have scored but, despite Ince’s curled strike from distance, it proved immaterial.