But in the Barcelona Open, O'Connell's fellow Sydneysider Alex de Minaur once again found his old nemesis Stefanos Tsitsipas too tough a hurdle as he bowed out at the quarter-final stage of the week's biggest clay-court event on Friday.
In Bavaria, O'Connell, fresh from his career-best triumph over German hero Alexander Zverev on Thursday, followed up 24 hours later by prevailing 7-6 (7-5) 4-6 6-3 in a quarter-final dogfight with Italian qualifier Flavio Cobolli.
It had been a freezing lunchtime when he downed Olympic champ Zverev, but the sun was out on Friday as O'Connell had to dig deep against the 20-year-old Cobolli, who'd already knocked out another Sydneysider Jordan Thompson earlier in the event.
The 28-year-old was left thrilled to prevail after nearly two and a half hours, overcoming a second-set let-down when he appeared to be struggling physically before finding new reserves of energy in the decider.
O'Connell had also been in trouble in the hour-long opening set, having to save three set points at 4-5 down before fighting back and eventually taking the tiebreak when Cobolli offered up the gift of a double fault at set point down.
His victory has given world No.82 O'Connell his first taste of last-four action in a tour-level event since he reached the semis in San Diego last September.
He will play Denmark's in-form top seed Holger Rune, who had no problems disposing of Chile's Cristian Garin 6-2 6-4 and it will now ake a monumental effort from O'Connell to earn the victory that would take him not just to his first final but also to a career-high ranking.Â
For de Minaur in Barcelona, though, it was just the same old story against Greek star Tsitsipas, who was simply too powerful while beating the Australian No.1 for the ninth successive time, 6-2 6-4.
The Sydneysider was never in the hunt once Tsitsipas broke his serve for 2-1 in the opening set and then quite dominated on the court named in honour of Rafa Nadal.
Confident at the net, winning 17 points there with his aggressive approach, and ruling from the back court too, Tsitsipas was also helped by uncharacteristic errors - 27 unforced mistakes in all - from the Australian, who only managed to get in 47 per cent of his first serves.
"I would say my shots were heavy, equally with forehand and backhand. I had the patience of a donkey today and I knew that was the foundation of the match," said Tsitsipas, who just seems to bring the worst out of the Australian.
13°C