Gajdosova, 25, had done her best to overcome a difficult 2012 by snapping up a wildcard and ousting world No.16 Roberta Vinci in the first round of the season-opening event.
And her luck appeared to have turned around when she avoided Sharapova in the second round after the reigning French Open champion pulled out with a collarbone complaint.
But Sharapova's replacement - lucky loser Lesia Tsurenko of the Ukraine - crashed the party at Pat Rafter Arena by ousting the Slovak-raised Aussie 1-6 6-1 6-4 in just over an hour and a half.
Gajdosova had been the last of the four-strong Australian women's contingent left standing in the Brisbane International.
Former world No.25 Gajdosova endured a horror 2012 in which injury ensured her ranking slipped 150 places to relegate her to No.183 - but it paled in comparison to her off-court fortunes.
Her nightmare year culminated in the death of her mother Jarmila due to throat cancer in September.
The power-hitting Gajdosova looked to be in control in the second-round clash with the world No.116 Tsurenko after cruising through the first set in just half an hour.
But the tables were quickly turned by the Ukrainian as she fed off the Australian's string of unforced errors to book a quarter-final showdown with Slovakian surprise packet Daniela Hantuchova.
Earlier, fourth-seeded German Angelique Kerber narrowly avoided becoming the latest big name to bow out in Brisbane by overcoming Puerto Rican qualifier Monica Puig 3-6 6-4 7-6 (9-7) in the second round.
World No.5 Kerber came back from 4-1 down in the third set and trailed 5-2 in the deciding tiebreaker before finally overcoming the plucky world No.124-ranked 19-year-old.
It abruptly ended a giant-killing trend in Brisbane which had already claimed five of the top eight women's seeds.
"It seemed like I was down 4-1 after five minutes (in the third set)," Kerber said.
"It was difficult. I had not seen her play before. It was a big surprise.
"It was tough physically. She (Puig) will be in the top 50 very soon."
And the United States' next big thing - world No.38 Sloane Stephens - overcame the woman who dumped Australia's Sam Stosur out of the Brisbane International, Sweden's Sofia Arvidsson, 6-3 6-4, in just over an hour on Wednesday to book a quarter-final showdown with third seed and idol Serena Williams.
The 19-year-old Stephens has befriended Williams in the US Fed Cup team and did not seem overawed by the prospect of taking on someone who has won 33 of her past 34 matches since a shock first-round French Open exit in June.
"I always was like, 'Oh, my God. I love her to death. She's amazing'," said Stephens about taking on the 15-time grand slam winner.
"Now she's like an actual person and I'm like, 'Oh, hi. How is it going?' She's not like a hero anymore - she's just a friend.
"Once we get out on the court, it is all business - anything can happen."