Kaia Kanepi, the nation's top tennis player, lost to an opponent over 100 places below her in the WTA rankings, committing 21 double faults in the process.
Kanepi (WTA 45) began the quarterfinal of the Hansol Korea Open in Seoul against Maria Kirilenko well, winning the first set 7-6.
Neither player showed particularly great skills, media reported, but Kirilenko prevailed, winning the next two sets, 6-2 and 6-3.
Kanepi has now lost all four times she has faced Kirilenko.
Estonian cyclist Peeter Pruus has received a 10-month ban for doping.
Pruus tested positive for trimetazidine on a four-day tour in Slovakia in June. The substance, which is usualy prescribed as a long-term treatment of angina, was only listed as a banned substance at the beginning of the year and Pruus said he did not know of the development. He has been using the medicine since 2011.
Pruus, who rides with the Rietumu-Delfin team, placed fifth in the Estonian national championships on June 27 and 12th in the Estonian road race championships on June 29th.