Begiristain will bring his trophy-laden 13-year association with the Citizens to an end in the summer of 2025 when he will step down from his post as sporting director.
The Spaniard originally planned to step back from day-to-day operations at Man City when he turned 55, but he became so invested in the club's project and working alongside manager Pep Guardiola that he extended his stay until his 60th birthday, which he celebrated in August.
After a successful spell at Barcelona, Begiristain joined Man City in 2012 in a move that reunited him with CEO Ferran Soriano, and he has since been a key architect of the club's rise to dominance in English football, with a total of 22 trophies won across seven different competitions to date during his time at the Etihad.
McInerney believes that Man City would not have been as successful without the presence of Begiristain, who successfully persuaded Guardiola to join the club nine seasons ago.
McInerney: 'Begiristain's Man City tenure littered with success'
Speaking to Sports Mole, McInerney said: "I think it's fair to say that the success that City have had probably doesn't happen without Txiki.
"I think Guardiola has gone on record [to say that Txiki was] the main reason that Guardiola joined Manchester City. I think he said if Txiki picked up the phone and he was calling from Chelsea he probably would have gone to Chelsea.
"Guardiola followed one of his best friends in football who sold him on the project. Manchester City's best part of 10 years under Guardiola just don't happen (without Txiki).
"He's the reason that we've had the greatest manager, in my humble opinion, of all time, because he has that close relationship of course as a former Barca player. They worked together at Barcelona and I think Soriano of course is involved with that as well.
"[Txiki is] a phenomenal sporting director. His time at Manchester City has essentially been littered with success, a whole bunch of wonderful signings. Some misses towards the end of his tenure, arguably, maybe in midfield the likes of [Matheus] Nunes and Kalvin Phillips haven't quite [paid off].
"But when you go back to early on - the likes of Fernandinho, an inspired signing, of course Kevin De Bruyne turned out to be one of the greatest, £50m spent now seems like a bargain in hindsight. Ruben Dias has only ever tasted Premier League success since he joined Manchester City - he's won a league every single time. Rodri became the best in the world. It takes a team to sign players, not just one person, but Txiki Begiristain is right at the heart of all this.
McInerney understands Begiristain's decision to move on
"He's had a phenomenal time building this squad and giving Guardiola the tools he needs to go and do what Guardiola does best - managing, coaching and out-thinking his rivals. I think he's been a phenomenal sporting director.
"It's impossible to be perfect. He could sit there and pull apart the odd mistake, but City have got better in certain aspects while improving the whole City Football Group, so to speak... it's all about his signings, but then we can [also look at] the turnaround in the market too, in terms of financially, the way that we're selling players now for a substantial amount of money.
"It sounds weird to sit here and celebrate a player going, but I'm not, I'm celebrating the business of it. Julian Alvarez for £14m, then for around £80m to Atletico Madrid two years later - it's really good business, it really is.
"I know City probably could do with a striker still, but little things like that keep happening where City make big profit on young players and that counts in 2024... that absolutely matters given the state of football these days with finance talk.
"Overall, he's done a really good job with the net spend and also winning trophies, but I understand why he might feel it's time to move on."
Man City to begin new era under Viana
Begiristain's successor Viana was allegedly identified by Man City as their 'favourite candidate' to become the club's new director of football and at the age of 41 has already forged a successful career behind the scenes at Sporting Lisbon.
After representing the likes of Sporting, Newcastle United and Valencia in his playing days, Viana spent six months as director of football at Belenenses before taking up the same role in 2018 at Sporting, where he has overseen a number of high-profile transfer incomings and outgoings.
One of the most notable arrivals in recent years is Viktor Gyokeres from Coventry City in the summer of 2023, with the Swedish striker developing into one of the deadliest strikers in Europe, and a possible move to the Premier League has since been mooted amid links with clubs such as Man City.
Discussing Viana's career at Sporting to date and comparisons with Man City's transfer business, McInerney said: "Looking at the sales and also the [transfer incomings] that Sporting have had - they've been a massive success.
"Obviously, Gyokeres from Coventry is inspired. He's scoring more or less a goal a game, a ridiculous record, a Haaland-esque record, [signed] for around £15m as well, an absolute bargain!
"People like Pedro Porro, obviously from Man City, then sold for big money to Spurs. Ousmane Diomande - another bargain signing. Pedro Goncalves as well... so many players that have done really well, and obviously there'll always be misses (failed transfers) when you're trying to build a squad. Guardiola had them early on as well (at City).
"It's usually of the sort of slightly cheaper variety as well. City early on had signings like Nolito and Claudio Bravo that didn't quite work out. They'd be a big deal for a lot of teams, but for Man City, because we had a little bit of money, like £10m, £15m here is not the end of the world. City were able to replace Claudio Bravo with Ederson for £30m a year later... I can't imagine it was quite as easy for Hugo Viana to go and do that (at Sporting). I think the odd miss will sting a little bit every now and then for them.
"I think it's probably not quite fair to hold Viana to the same level (as Begiristain) in terms of success rate, but having said that, he's still got an awful lot of success in the transfer market. He's obviously got a good eye for talent Hugo Viana.
"I do think there's something to be said as well for someone younger coming in," McInerney added. "I personally remember Hugo Viana as a football manager wonderkid. That was my experience from years ago on Championship Manager. That was a name I was very familiar with from those days."
What will Viana bring to Man City as director of football?
McInerney has acknowledged that Viana has big boots to fill in replacing Begiristain at Man City, but he feels that the individual qualities the Portuguese will bring to the director of football role can benefit the Citizens going forward.
"He's only young still. He's in his [early 40s]. He will bring a different sort of energy," said McInerney. "I think that hunger, that ambition is absolutely necessary. I think there's no denying that City are facing down a sort of transition after Guardiola. Hopefully Guardiola will be there for a little bit longer, but this new sporting director is going to oversee that.
"I really don't believe you can just try and copy what Guardiola has done. I think there's no point. As much as I'm cautious about a drastic change in playing style under someone like [Ruben] Amorim (someone who could potentially replace Guardiola if he decided to leave City next summer), I also appreciate at the same time that you can't just go 'keep doing what Guardiola does' because there's no one like him.
"It's going to have to be something a little bit different while hopefully keeping some of the identity, so the players transition nicely to the new manager.
"...I think City will be aware of just trying to mimic and imitate those years (of success Guardiola has had at Barcelona and Man City with Begiristain) because it' just not possible.
"You have to be pragmatic, you have to move on, you have to try something different, and Hugo Viana will bring energy and ideas, he'll bring his own style and he'll bring a different type of signing - that could be a good thing for City".
Man City - who face Sporting in the Champions League on November 5 - have confirmed that Viana will begin his full-time role as the club's director of football in the summer of 2025, but "will collaborate with Begiristain in the preceding months to ensure a smooth transition."