But the "good on yer, mate" Aussie accent only offered a thin disguise when he awkwardly stumbled through an unwanted press conference after his country's thrilling second Test win over South Africa last week.
In comparison to Gillespie the public speaker, however, there is nothing ungainly about Gillespie the fast bowler. His run-up is fluid and aggressive before he hits the crease with a thumping left foot. His action is upright and wickedly side-on. In short, Gillespie looks the genuine article. He is young and lithe, athletic and strong. He is also very quick. Australia are already counting their blessings and it will be no surprise if England are left counting their wickets in this summer's Ashes.
At Port Elizabeth, South Africa felt the power of Gillespie, who in only his fourth Test match on the usually benign St George's Park strip, exploited a deliberately prepared green wicket to return match figures of eight for 103. The South Africans shot themselves in the foot, manufacturing a track for their own four-man pace attack only to see Gillespie and Glen McGrath rip out their top order on the very first morning.
Gillespie manfully attempted to play down his first five-wicket haul in Test cricket. He apologetically explained: "The wicket did help me a lot but to be honest I did bowl a bit too short. Luckily I just got my line right and that got me out of trouble. I did feel my rhythm starting to come back for the first time in a long time but I wasn't flat out.
"I still don't feel comfortable in Test cricket. I haven't been around long enough yet. It's all a bit strange to be out there opening the bowling for Australia. I'm so aware of the responsibility. I don't want to let anyone down."
A return of five for 54 from 23 first-innings overs suggests otherwise. Indeed, that analysis does not tell the whole story. Gillespie had two sitters put down in the slips and two perfectly good catches by Ian Healy turned down by very ordinary umpiring.
Gillespie confirmed: "Those incidents did fire me up, I suppose. I'm never going to have a go at guys who drop catches or umpires who don't give me the nod. I guess I've learned that much already. Our coach, Geoff Marsh, has taught me so much. I'd forgotten a few things but Geoff soon put me straight and it showed in the way I have been bowling on this tour. There's always room for improvement but I'm getting there. I know I can bowl even quicker but that will come."
The Australian captain, Mark Taylor, is well aware of the importance of Gillespie's sudden explosion on to the Test scene.
"Jason has given us an added edge because we are now able to go in with just two specialist seam bowlers. When the quicks need a blow I can call up our spinners, Shane Warne and Michael Bevan. It means we can attack from both ends all the time," Taylor said. "I believe this is the best Australian side I've played in. We are an even better balanced team than the one in the West Indies two years ago - and, dare I say it, we appear to be getting better with every game."
Gillespie and McGrath are clearly equipped to take their place eventually in Australia's fast bowling hall of fame. Up there with the best: Lindwall and Miller, Lillee and Thomson, perhaps Hughes and McDermott. Not too bad for a 21-year-old. Earrings and all.