But since then old wounds have opened up once more, with shots fired in public interviews that reveal an apathy between the two that developed in the months before and after Walker’s £54 million ($70m) move north in 2017.
“Manchester City have paid a lot of money for Kyle, like they have signed different players to try to get success in the future," Pochettino told reporters that summer, after showing them the Whatsapp message in question.
“There’s no doubt he will succeed at City. But for me, I think we saw the best Kyle with Tottenham.”
Hardly the words of a man at peace with the past. That observation also turned out not to be true, given Walker’s starring role in City’s 100-point Premier League title win in his first season at the Etihad Stadium.
And in his book Brave New World, which serves as his diary of the 2016-17 season, Walker’s last at Spurs, Pochettino also put across his version of the right-back’s desire to leave.
“Gaffer, I’ve been at Tottenham for nine years," Walker says, according to Pochettino. “I’ve thought about it and my heart isn’t here anymore. Nor is my head. I’ve given all I have to give. I wanted to tell you before I tell my agent that I want to leave this summer.”
Pochettino says he reminded Walker to stay professional for the final six weeks of the season, to which he supposedly replied: “OK, gaffer. But it’s already decided.”
The Argentine also said he was “convinced that his people are leaking stories to the press.”
That particular version of history only came to light some months after the two exchanged messages.
Walker does not think much of Pochettino these days, but he was careful with his words when he sat down with the press earlier this season.
“I was hurt a lot by that,” Walker told the Daily Mail last September. “He said his door was always open and I thought it was a private meeting we had. So, I kept quiet but then he went and wrote about it... or his version of it.
"If he was going to do that he might as well have called a press conference and told everyone. He told one side of the story, but it’s a side of a story I don’t agree with.
“He said he had a witness in there, but he didn’t tell the correct story, no way.”
Walker says he actually wondered whether he had made the right choice once he had signed for City, but that his lack of playing time at Spurs was a big factor in his decision, as was a desire to “get my hunger back... discover something different”, “prove I could do this somewhere else”, and move back up north, closer to his mother’s home city of Sheffield.
No matter who you listen to, however, both sides have left out many details that ultimately led to Walker’s exit.
One factor is that Walker knew he could significantly improve his wages of £70,000 ($91,000) per week if he were to move elsewhere, at a time when many members of the Spurs squad were complaining about their pay packets.
But central to the row is that Pochettino did not believe that the England international was fit enough to play a game every three days, which Walker always disputed - and eventually disproved in his first season at City.
Pochettino felt Walker (and Danny Rose), did not work hard enough in training and had doubts about the right-back’s professionalism; one of the only other mentions of Walker in the Spurs boss’ book tells of how he turned up late for a team meeting during the summer of 2016, which was the “trigger” Pochettino needed to “tear into” the group over their finish to the previous season.
Another point of contention was a foot injury Walker sustained, which he said he sustained while walking his dog. Pochettino, however, had been told it happened while Walker was drunk on a night out.
Walker says Pochettino “taught me to look after myself, eat right and rest”, but eventually the Argentine grew to mistrust his player, and in that final season together Walker did not play any of Spurs’ away Champions League matches.
Walker was livid at this development and the relationship deteriorated as the season went on, with Pochettino eventually introducing Kieran Trippier at right-back for the final games of the 2016-17 season.
Ultimately the transfer suited all parties; Walker got his move, Spurs argued that Trippier was a ready-made replacement, and after months of incredibly frustrating talks for City, the Londoners received an up-front fee of £50m plus £4m in bonuses. A City source close to those lengthy negotiations said that dealing with Daniel Levy was "like blood in your p***".
Danny Rose also sought a move soon after Walker’s exit and eventually gave a much-publicised interview criticising the club’s wage structure. Had he not done so, other team-mates would have.
Yet Walker remains the only high-profile player to have left Spurs in recent years, proof not only of how difficult it is to negotiate with Levy, but of just how strained the relationship between Walker and Pochettino had become.