With there being just a 49-hour gap between the end of City's pulsating 2-2 draw with Arsenal in the Premier League on Sunday and the 19.45pm kickoff against Watford, the Citizens have little time to rest and prepare for this cup contest.
Guardiola stated earlier this month that he intends to "select two teams" against Arsenal and Watford due to the quick turnaround, with any of those players who participated for a significant chunk of the draw with the Gunners to be given a rest if possible.
Man City will be without four players due to injury including star midfielders Kevin De Bruyne and Rodri, the latter of whom could reportedly be ruled out for the rest of the season with an ACL injury sustained in the clash with Arsenal.
Guardiola has confirmed that De Bruyne - who picked up a groin problem in the 0-0 Champions League draw with Inter Milan last week - will not be ready to return to face Watford, but he 'does not think it will be long' before the Belgian in back in action.
Nathan Ake (muscle) and Oscar Bobb (leg fracture) are also in the treatment room, meaning Guardiola will only have a limited amount of senior players to select from, with the Catalan set to call upon some of the club's academy stars to step up to the first team.
Pep Roulette to be in full swing for Watford clash?
McInerney has pointed out that Guardiola's pool of academy players to choose from is "quite small" following the departure of several youngsters either on loan or permanently this summer, so some senior stars who featured against Arsenal may be required to play again on Tuesday.
Speaking exclusively to Sports Mole, McInerney said: "Guardiola has a trend of only really using academy players that he's looked at in pre-season. Obviously there are exceptions, but he usually picks from a pool of players that he's worked with, and the pool this season is quite small because a lot of them have left the club [permanently] or on loan.
"Micah Hamilton went to Middlesbrough, Callum Doyle went on loan to Norwich - doing really well there - there are quite a few players who have gone. All we've been left with is 17-year-olds and City play with a young Under-21s side.
"I think it's going to fall on a couple of senior players to play again, which is not ideal after a game like that (against Arsenal), but I don't think we've really got much choice unfortunately."
Discussing which senior and academy players could play against Watford, McInerney said: "[James] McAtee, of course, he's an academy player, but he's [now] a Premier League footballer, so he's obviously going to start.
"Nico O'Reilly played a lot in pre-season. He played in the Community Shield and I think he would probably play. Josh Wilson-Esbrand - a left-back that I thought would probably leave on loan, but he hasn't left the club yet. I presume he'll start at left-back, because he's got no choice. [Josko] Gvardiol cannot play again with Nathan Ake out.
O'Reilly, Wilson-Esbrand, Wright in contention for first-team outing?
"Wilson-Esbrand started pre-season friendlies really poorly, but improved the more he played, so I think there's a little bit of quality there, and he's played Championship football, so he's definitely got enough quality to play in a game like this.
"John Stones I think will start. Rico Lewis will start. Matheus Nunes you would think is almost a lock. I wouldn't be surprised if [Mateo] Kovacic plays again, because [City are] probably going to need him. [Jack] Grealish, [Phil] Foden, [Stefan] Ortega will probably get a start in goal."
Eighteen-year-old Jacob Wright could also be in contention to feature, a highly-rated academy start who has contributed to five goals (two goals, three assists) in his opening three Premier League 2 matches this season, and has also been compared to Arsenal midfielder Jorginho.
"[He is a] really compose midfielder. He gets compared to Jorginho a fair bit at City," McInerney added. "[For] experience, Guardiola likes to have him in and around the team an awful lot, so definitely (he could play)."
On McAtee, McInerney spoke to Sports Mole last week about how the 21-year-old could be the man tasked with operating as a false nine and replacing star striker Erling Haaland when he is given a rest, and he sticks by that opinion.
"He'll almost certainly (play against Watford)," he continued. "We have no choice and it's these kind of games that he should be playing in, even if we did have a choice.
McInerney: 'McAtee is a brilliant little playmaker'
"I was thinking even him on the pitch (against Arsenal) would have been better than [Ruben] Dias taking 25 shots, because McAtee is a highly technical, brilliant little playmaker. I do understand why you wouldn't [play him] in a game of that magnitude, but I was thinking: 'I wish we had someone like him on the pitch'.
"McAtee is brilliant and I hope that these enforced changes gives the likes of McAtee [a chance to stake a claim] for more regular involvement, because he's a really gifted footballer and he's one that Guardiola convinced to stay (in the summer).
"He'd been on loan at Sheffield United for two seasons, and there has been a feeling that if you've been away on loan from City you probably don't come back into the team, because the standards are so high, but Guardiola really likes McAtee and City really rate McAtee.
"Guardiola has been very complimentary about what he could have learnt playing for a relegation-battling team in the Premier League. He said, and I'm paraphrasing: 'It sort of makes a man of you'. You've got to learn how to play when the entire club's existence in the Premier League is on the line - you can't not learn from that.
"McAtee is more than ready to be involved every now and then. I think throughout the course of the season, given how long it's going to be, McAtee and players like him will be really important."
Man City will endeavour to avoid crashing out of the EFL Cup third round for the second successive season after losing 1-0 to Newcastle United - their Premier League opponents on Saturday - this time last season.