It was Kristyna's first win over a top-five ranked player and she will go on to play fellow Czech Barbora Strycova in the quarter-finals.
Naomi Osaka continued her stunning run of form with a 6-3, 6-2 victory over 23-times Grand Slam champion Serena Williams in the first round of the Miami Open on Wednesday, the latest big win for the 20-year-old Japanese player.
List of Australian Open men's singles champions since the event began in 1905 (Australian unless stated):
Fifth seed Maria Sharapova averted an early exit on a sweltering day in Flushing Meadows. Updates from Wednesday's play.
The Australian Open has seen many unheralded players punching above their weight. Rediff.com takes a look at a few such unseeded players who went the distance in the new millennium.
Cilic's booming serve lacked its usual accuracy and Germany's Kohlschreiber was able to control long rallies, pushing the towering Croatian around the court with pinpoint groundstrokes en route to a quick victory.
Photos of Day 5 of the Australian Open being played in Melbourne
Third seed Rafael Nadal battled through mid-match cramps for more than an hour before he lurched into the third round of the Australian Open with a 6-2, 3-6, 6-7(2), 6-3, 7-5 victory over American qualifier Tim Smyzcek.
A dominant Rafael Nadal arrived at one career milestone on Thursday but the speed of the Spaniard's rampage through the early rounds of the French Open suggests his eyes are fixed firmly on another more significant one.
Second seed Angelique Kerber stayed on track in her quest to unseat Serena Williams as world number one by beating Mirjana Lucic-Baroni of Croatia 6-2, 7-6(7) on Wednesday to reach the third round of the US Open.
Roger Federer glided to victory on another hot, steamy day at the US Open, the envy of a clutch of men's players made to work overtime on Tuesday at the season's final Grand Slam.
List of Australian Open men's singles champions since the event began in 1905 (Australian unless stated):
Rafael Nadal easily avoided the embarrassment of a back-to-back first round exits at the Australian Open on Tuesday, ramping up his serve and rattling off 39 winners to beat Florian Mayer 6-3, 6-4, 6-1 on Rod Laver Arena.
IMAGES from Day 3 of the US Open in New York on Wednesday.
It was job well done for Novak Djokovic as he silenced Bernard Tomic and his Australian Fanatics with an emphatic 6-3, 6-3, 6-3 victory in the Wimbledon third round on Friday.
PHOTOS from day four of the Wimbledon championships at the All England Lawn Tennis and Croquet Club in London on Thursday.