Top seed Alisa Kleybanova crashed out of the GDF Suez Grand Prix in Budapest on a bad day for the well-fancied players.
The Russian was beaten in straight sets by experienced Swiss Patty Schnyder - who extended her perfect record against the 20-year-old to four wins in as many matches, the most recent coming in the quarter-finals of this tournament last season.
Kleybanova was accurate with 89 percent of first serves but won just 56 percent of the ensuing points, with Schnyder breaking twice in the first set and once in the second - when Kleybanova failed to take advantage of eight break points - to triumph 6-4 6-3.
China's fifth seed Shuai Peng was another casualty as she was routed 6-1 6-1 by unheralded Latvian Anastasija Sevastova.
The 20-year-old would have drawn confidence from March's win over Peng at the Estoril Open and four aces and five breaks of serve helped her round out a 48-minute procession.
She now faces the winner of the clash between Anna Chakvetadze and second seed Alexandra Dulgheru, which was suspended due to darkness after going into a third set.
Chakvetadze broke at the first opportunity but Dulgheru levelled and took the first set in a tie-breaker (7-5). She again dropped serve in the first game of second set, though, and was unable to recover this time as the Russian took the set 6-1 to level the match.
Eighth seed Polona Hercog survived the exodus, although the Slovenian was forced to come from a set down against Colombia's Catalina Castano.
The South American won a topsy-turvy first set 6-4, with three breaks to two, but Hercog battled back to prevail 4-6 6-4 6-4 in over two-and-a-half hours.
Meanwhile, top seed Flavia Pennetta eased into the quarter-finals of the Swedish Open in Bastad with a crushing victory over Sloane Stephens.
Pennetta, the world No.12, took just over an hour to beat American wildcard Stephens 6-1 6-1 to continue her flying start to the tournament where she has lost just four games and spent only an hour and 49 minutes on court.
The 28-year-old will now meet American Jill Craybas who came from a set down to beat Anna-Lena Groenefeld 3-6 6-0 6-4 and reach her first quarter-final of the year.
Second seed Aravane Rezai beat Renata Voracova 6-4 6-2 while No.5 seed Arantxa Parra Santonja held off qualifier Nuria Llagostera Vives 6-4 6-3.
Lucie Safarova, seeded third, did not have quite as straightforward a route to the last eight as she faced break points for a 6-2 2-0 deficit before rallying to beat Karolina Sprem 2-6 7-5 6-3.
Fourth seed Gisela Dulko was pushed as well, rallying from 5-2 down in the third set and saving four match points en route to a 6-2 1-6 7-6 (7-1) win over Tatjana Malek.