Warren recalls being paired with McIlroy at Walton Heath in a US Open qualifier. "I think he was about four at the time," joked the Scot. That was in 2008 when the 19-year-old McIlroy was already destined for greatness. Both failed to get through to Torrey Pines, scene of Tiger Woods' last major victory.
Now the duo, separated by 188 places in the rankings, are tied for the halfway lead with Luke Donald, the world No.2, at the DP World Tour Championship, having reached an 11-under aggregate of 133.
A massive first prize of almost £840,000 is in offer and while it could be McIlroy's fifth victory of the season or Donald's fourth – and second in a row – the former World Cup winner Warren is hoping to end more than five years without a title.
"Everyone knew from day one that Rory was special and I'm really looking forward to it," said the 31-year-old after outscoring Donald, a 2001 Walker Cup team-mate, by one with his second round of 67.
That may have just delayed a head-to-head clash between golf's top two for 24 hours, but Warren takes great heart from how he performed. "Little things like that, it does wonders for your confidence," he added. "It's going to be a great weekend. The atmosphere is buzzing already so I'm looking forward to seeing what it's like tomorrow and Sunday as well.
"It's nice to be the Scot with the Englishman and the Northern Irishman. It's a high-quality leaderboard and doesn't get any better in the world really."
McIlroy also managed a 67 after fighting with what he thinks was a touch of sunstroke following his opening 66.
"When I came off the course I had a really sore head and fever," he said. "I just took painkillers and Caroline [Wozniacki, his girlfriend] squeezed about five lemons into a glass and I took that.
"I had some sort of vitamin and mineral drink too. It made me a feel a little bit better but, with the anti-doping and all that, we can't really take much."
Donald lost the outright lead with his 68, but still has a chance to be the first player since Jesper Parnevik in 1995 to go through a European Tour event without a bogey.
Only a stroke behind are South Africans Louis Oosthuizen and Branden Grace, the latter chasing an incredible sixth victory since coming through last December's qualifying school.
Richie Ramsay, paired with Martin Kaymer, hit a 68 for a share of sixth on 135. "If I could take a little bit of Martin's mental game it would help me so much," admitted Ramsay, after gathering some tips from the German.
Scott Jamieson finished in the top 20 on 137 with Stephen Gallacher a stroke further back on 138. Paul Lawrie, runner-up in Dubai this time last year, had to settle for a 72 and is joined by David Drysdale on the 143 mark.