Speaking ahead of this weekend's Champions League final, Kroenke described a discussion with Mertesacker, who was a year into his role as the club's academy manager at the time, that led directly to the signing of William Saliba.
"I had a great conversation with Per Mertesacker," Kroenke said. "After the final in Baku I made a comment about Virgil van Dijk, who had arrived at Liverpool a year or two before. I said: 'How do we get one of these guys into our system?'"
Mertesacker's response was blunt: unless Arsenal had £100million available, van Dijk was not a realistic target. Kroenke then asked who the best young defender in Europe was.
"He turned without hesitation and said William Saliba."
Arsenal signed the then-18-year-old centre-back from Saint-Étienne that summer. Saliba was immediately loaned back to his former club and then to Nice and Marseille over three successive seasons before Mikel Arteta made him a cornerstone of the first-team defence.
Kroenke has since found out that even within the club, Saliba's arrival was met with quiet scepticism. He admitted the episode was only shared with Arteta long after the fact.
"Mikel and I have now laughed about this because I didn't tell him the story until much later," he said. "When we purchased William and he went on loan for two seasons, then we were transitioning to Mikel by the time William rejoined us, there were some thoughts on the front end about William rejoining our squad that were very well covered. I'll let you guys fill in all those blanks.
"I was sitting over in America laughing, going, 'Please let this kid work out!' I was never going to say, 'Hey, someone told me a few years ago that this kid was going to be great!' What am I going to do? No."
Kroenke was careful to frame his involvement within its limits. He does not consider himself a figure in the transfer process, describing his role as understanding the reasoning behind decisions rather than driving them.
"I don't get involved in transfers," he said. "I think my job is to understand the 'why' on the front end, so there's accountability on the back end if it goes wrong."
Arsenal's Europa League final defeat to Chelsea in Baku had come at the end of a difficult period that would soon deepen. Manager Unai Emery was sacked six months later, and a supporters' protest movement — built around the message "We Care, Do You?" — was gathering force against the Kroenke family's ownership.
That same summer, Saliba arrived as one of several foundations being quietly laid for what would become a transformed club. Bukayo Saka and Gabriel Martinelli were also moving into the first-team picture at around the same time.
The arc from that low point in Baku to the Premier League title is not one Kroenke tells without acknowledging what was at stake. The Saliba tip from Mertesacker was one decision among many, but it was the one he chose to tell first.