Phillips was an integral cog in Marcelo Bielsa's machine as Leeds secured promotion to the Premier League in 2020, before establishing himself in the top flight and playing a key role for England en route to the final of the COVID-delayed Euro 2020 a year later.
The Yorkshireman's stellar form caught the eye of several top Premier League clubs, but it was champions Manchester City who decided to fork out an initial £42m to recruit the midfielder in the summer of 2022, following the departure of Fernandinho.
Phillips was "long admired" by Man City according to director of football Txiki Begiristain, who upon the midfielder's arrival labelled him a "formidable talent" and a "superb addition" to Pep Guardiola's squad who has the credentials to "complement our game perfectly".
A switch to the Etihad Stadium was considered by many as the perfect step for Phillips in his career, with the midfielder excited by the prospect of developing his game under Guardiola, a deep-lying maestro in his playing days, but it is now fair to say that his time at Man City has been a major disappointment.
Phillips arrived at Man City with a shoulder injury and was subsequently reduced to just four appearances in all competitions before being labelled "overweight" by Guardiola after returning from England duty at the 2022 World Cup in December of that year.
Injury woes and the exceptional form of midfield lynchpin Rodri ultimately forced Phillips to play second fiddle to the Spaniard, who is considered "unique" by Guardiola and the best player in the world in his position.
Despite starting just four of his 21 appearances in all tournament during his first season at Man City - a historic treble-winning campaign for the club - Phillips expressed his desire to stay at the Etihad and fight for his place under Guardiola after a frustrating injury-hit 12 months.
However, Phillips's fortunes did not improve last season, as he played just 89 minutes of Premier League football and failed to make a single start during the first half of the campaign.
It quickly became apparent that the midfielder was deemed surplus to requirements by Guardiola, who tweaked his ever-evolving Citizens philosophy and opted to start the likes of John Stones, Manuel Akanji and Rico Lewis - all natural defenders - in a hybrid midfield role ahead of the Yorkshireman, whose backside was firmly glued to the substitutes' bench.
Phillips future uncertain after dismal West Ham loan
Not long after Phillips turned 28, the decision was made by Man City to send the midfielder out on loan for the second half of the 2023-24 season in search of regular first-team football, with West Ham United winning the race for his signature in January.
After finalising his move to the Hammers, Phillips admitted that he felt "useless" during his frustrating time away from the Man City first team and was left "very sad" when he knew that "the next step had to be to move on".
West Ham had high hopes that they could get the best out of Phillips and reignite his career, but he instead endured a torrid temporary spell at the London Stadium, with his below-par performances across 10 outings leading to widespread criticism from the Hammers fanbase.
Unsurprisingly, Phillips was left out of the England squad for Euro 2024, and West Ham opted against activating the reported £40m option-to-buy clause that had been inserted into Phillips' loan agreement, with the midfielder having since returned to the Citizens with his future shrouded in uncertainty.
Does Kalvin Phillips have a future at Man City?
Phillips was selected in Man City's pre-season squad - a depleted one due to the extended breaks given to several first-team stars following their international exploits earlier this summer - for their tour of the United States.
To the surprise of some, Phillips featured in all four of City's friendly fixtures against Celtic, AC Milan, Barcelona and Chelsea, starting three of those games and playing for a total of 266 minutes - in comparison, Phillips was handed 306 minutes of action for the Citizens in all competitions in the first half of last season.
Phillips, who has worked hard throughout pre-season to get himself in the best possible shape, began the tour operating as a midfielder, but he started City's final two friendlies against Barcelona and Chelsea as an unorthodox centre-back, impressing in both matches particularly with his range of passing.
Guardiola recently discussed Phillips's future and explained why he played in defence, telling reporters on July 31: "I do not know what is going to happen with his situation.
"He was really good for the problems we had. I know Kalvin when he gets the ball and can see all the pitch in front of him he's a really good player. When he has the small spaces there are more problems.
"That's why, with the problems we have, he makes an incredible effort with his position. He was confident with the ball and helps us a lot. I'm really pleased with his performance.
"When we have all our central defenders, we have a lot of central defenders. That's why it's not his position. We will see. Now he's helping us and it's good for us."
Although Phillips has impressed in pre-season, it is understood that the midfielder's form will not be enough to convince Guardiola to reintegrate him into City's first-team squad for the new season, and the Citizens will instead look to move the Yorkshireman on either on loan or permanently this summer.
Man City already have a wealth of options in defence and - as previously alluded to by Guardiola - Phillips has only played in the centre-back role due to the absence of Stones, Akanji, Ruben Dias and Nathan Ake, while teenage midfielder Nico O'Reilly has emerged as a breakout star during pre-season and could therefore push Phillips even further down the pecking order.
What next for Phillips? Which clubs could he join this summer?
According to Sky Sports News, Phillips is open-minded about his future, but as things stand, there have been no firm developments regarding a potential exit from Man City.
A number of clubs both in England and abroad are believed to be monitoring Phillips's situation, but it is understands that Turkish giants Galatasaray are not currently on the list of options the midfielder has.
It has previously been reported that Everton are one club exploring the possibility of signing Phillips, with the Toffees known to be on the lookout for a new midfielder following the £50m departure of Amadou Onana to Aston Villa.
A move abroad has also been mooted for Phillips, with the likes of Roma, RB Leipzig and Red Bull Salzburg all being credited with an interest, but it is thought that Everton are the club who have shown the most desire to recruit the midfielder this summer.
Man City would prefer to sell Phillips this summer and are keen to recoup as much of the £42m they spent on the midfielder two seasons ago, but Everton would prefer to negotiate a season-long loan deal due to their financial predicament.
Everton an ideal club for Phillips to reignite his career
The Citizens' current stance on Phillips - who still has four years remaining on his £150,000-a-week contract at the Etihad - is subsequently proving to be a stumbling block for interested suitors such as Everton.
However, with the Premier League champions known to be keen to get their No.4 off of their books, it is thought that their terms could soften towards the latter stages of the transfer window, making the midfielder a more affordable option to cash-strapped Everton.
A proposed move to Sean Dyche's Everton for Phillips has been backed by former Toffees scout Bryan King, telling Goodison News: "I would think that a player like that would do well at Goodison Park.
"He is a gutsy player who works hard, and fights for every ball, he is the type of player who Everton supporters love. It would be fantastic to see him resurrect his career and get back to his previous levels."
Having now entered the prime years of his career, Phillips can ill-afford another season watching on from the sidelines and a move to a club like Everton, where he would presumably be assured regular first-team football, would make a lot of sense.
With just under four weeks of the transfer window remaining, Phillips's future is certainly one to watch.