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Pep Guardiola's side had routed the same opponents 8-0 just over a year ago and demolished League One outfit Exeter City 10-1 in this season's third round, but they were made to work by Karl Robinson's team, who are sixth in League Two.

City only needed six minutes to go ahead, with Rayan Ait-Nouri flashing in a low cross that Alfie Dorrington diverted into his own net, though that goal did not open the floodgates as Salford dug in, and the hosts saw centre-back Max Alleyne limp off injured.

It should have been 2-0 when Omar Marmoush found the top-left corner with a thunderous volley across goal, only for the flag to go up. Though replays showed the Egyptian was clearly onside, VAR is not in use until the fifth round of the FA Cup, so the on-field decision of no goal stood.

Salford could even have gone into half-time level, but James Trafford kept out Ben Woodburn's half-volley, and Brandon Cooper headed wide when totally unmarked.

And Salford continued to push forward after the restart, with Kelly N'Mai working Trafford at his near post, but the growing nerves among the home fans were settled in the 81st minute. 

A quick free-kick released Rayan Cherki to the byline, and when his cross-shot was parried by Matt Young, Guehi, who replaced John Stones as a 65th-minute substitute, was on hand to tap into an unguarded net.

Fellow substitute Antoine Semenyo rattled the far post late on, but City were unable to add further gloss to the scoreline.