Sydneysider O'Connell had been hoping to make his first semi-final in an ATP event for two years in Bucharest on Friday but the world No.87 found Fucsovics in inspired mood as he blasted past the Australian 6-0 6-4 in an hour and 18 minutes.
For a set-and-a-half, the 30-year-old O'Connell didn't do much wrong, but was simply blown away by the Hungarian, who had decided to go for broke with his shotmaking, hoping to avoid another long slog after suffering muscle cramps in his previous day's marathon win over Argentine Mariano Navone.
O'Connell, who'd also needed a medical timeout on Thursday with an apparent hip injury in his last-16 win over fourth seed Nicolas Jarry, couldn't even get a game on the board in the opening set as Fucsovics blasted 12 winners past him.
He did well to regroup after going 4-2 down in the next set and recovered to 4-4 before another loose game as he served to stay in the match enabled Fucsovics to wrap up an eighth successive match at Bucharest's National Tennis Centre.
For O'Connell, it was a fairly chastening end to his bid to become the first Australian semi-finalist at the event since Richard Fromberg won the tournament in 1997 but it had at least been a good week's work to give him confidence going into the rest of the European claycourt summer.
Fucsovics will next face top seed Sebastian Baez, the Argentine clay-court specialist who knocked out his compatriot Francisco Comesana 7-6 (7-5) 2-6 6-1.
Rising 22-year-old Italian Flavio Cobolli beat Austrian qualifier Filip Misolic 7-6 (7-5) 6-4 to set up the other semi against Bosnian Damir Dzumhur, who led second seed Pedro Martinez 6-1 2-0 when the Spaniard had to retire with an upper leg injury.
