The German outsider, given an unexpected second chance through another player's withdrawal even though he'd already himself been eliminated in the qualifying rounds, was this time unlucky to find the on-song Australian No.1 in ruthless mood in their quarter-final on Friday.
It took the Sydneysider less than an hour and a half to dismantle the world No.93 in straight sets, 6-1 6-4, to proceed to the semi-final for the second-straight year in the indoor hardcourt tournament that's proved a happy hunting ground for him.
De Minaur is seeking to reach the final again after his defeat to Jannik Sinner in last year's championship match.
But he's doubtless next face a rather harder task in Saturday's semi-final against either Stefanos Tsitsipas, the Greek who owns an 11-1 winning record against him, or Italian Mattia Bellucci, who were meeting in the next quarter-final at the Rotterdam Ahoy arena.Â
De Minaur has been in sharp form all week in his first tournament since reaching the quarter-finals of his home grand slam at the Australian Open, and has swept into the last four without dropping a set.
Indeed, he has only had his serve broken once all tournament, with Altmaier summoning up some laudable resistance in the second set to crack the world No.8's delivery.
But de Minaur, with his inside-out forehand working sweetly and proving effective with his regular forays to the net, hit back immediately for a fourth break of serve at 4-4 that effectively sealed the German's fate.
He grabbed the break with a fabulous point that ended with de Minaur powering a smash towards Altmaier's body, leaving the German to end up tossing his racquet away in despair after wondering what more he had to do to penetrate the Aussie's superb defences.
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