The unsung Sydneysider, who's had his best-ever season, still wasn't expected to eclipse his country's big two, Nick Kyrgios and Alex de Minaur, at the grass-court grand slam.
But after last year's finalist Kyrgios didn't make the start line with injury at the weekend and then de Minaur was left disconsolate at a thrashing by Matteo Berrettini on Friday, world No.73 O'Connell is the last Aussie standing in the third round.
With Jason Kubler also bowing out in the second round later on Friday, O'Connell is the only survivor of the original 10 Australians in both the men's and women's draws.
And the big smile on his face after he defeated Czech left-hander Jiri Vesely 6-3 7-5 6-4 demonstrated that all the years of sacrifices and hardship had been worth it for a victory that's taken O'Connell into the last-32 of an overseas grand slam for the first time and propelled him towards the game's top 50.
"All the odd jobs I've worked at," reflected the 29-year-old, thinking of the time he would have to supplement his tennis dreams with part-time work.
"Boat cleaning, working in clothes shop, tennis coaching, delivering flyers ... I think back on those, and I'm like, 'Wow, now I'm here!'"
His cheque for getting through just two rounds is Stg 85,000 ($A163,000) but O'Connell reckoned it wasn't money, but his rise up the rankings that really enthused him.
"This time last year, getting to the top-100 was a huge goal of mine. So to be sitting here a year later, looking at top-50, that's awesome," said the man who will rise to the cusp of the top-50 if he can beat American Christopher Eubanks, victor over Briton Cam Norrie, on Saturday.
But while O'Connell celebrated his equal-best result at a grand slam, having also reached the Australian Open third round last year, the country's No.1 de Minaur looked wholly despondent after being swept away 6-3 6-3 6-4 by the rejuvenated 2021 finalist Berrettini.
Kubler, struggling physically with a hamstring problem, produced a gutsy display against Chilean No.25 seed Nicolas Jarry before he finally went down 7-5 5-7 6-3 6-4, leaving O'Connell out there on his own.
It was another encouraging milestone for the self-confessed "late developer" O'Connell, who's enjoyed a big year with success on the clay, reaching the semi-finals in Munich including a victory over Alexander Zverev, and now a major breakthrough on the grass.
He had endured a tough first-round match, which stretched over three days because of constant frustrating rain delays against Serbia's Hamad Medjedovic, but the win over the dangerous Czech southpaw Vesely, who has a fine Wimbledon record, in the bright sunshine of Court 14 proved surprisingly routine.
Meanwhile, over on Court 18, a top-16 seeding was supposed to keep the No.15 de Minaur away from the top players, but Berrettini, whose injury woes including a recent abdominal problem had left him unseeded, looked back to his formidable big-serving best.
The Italian was in coruscating form as he hammered 38 winners and won 88 per cent of his first serves, with de Minaur ekeing out three break-point chances, all of which were quickly wiped out.
"This defeat will obviously sit with me for a while. Yeah, I'm not happy at all. It's a pretty bad situation to be in," said a despondent de Minaur, who'd been looking for a big run after finishing runner-up at Queen's Club.
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