MELBOURNE (Reuters) - Australian Open champion Sofia Kenin was unable to bear the pressure of defending her maiden Grand Slam title as the American bowed out in the second round in tears on Thursday following a 6-3 6-2 loss to Estonia's Kaia Kanepi.
Kenin, who was also runner-up at the French Open last year, crumbled in 64 minutes and the 22-year-old admitted the burden of expectation took its toll.
Fourth-seeded Russian Daniil Medvedev celebrated his 25th birthday in style with a 6-2 7-5 6-1 win over Roberto Carballes Baena while Rafa Nadal overcame the challenge of Michael Mmoh as well as an unruly spectator in a 6-1 6-4 6-2 victory.
Heavily bandaged top seed Ash Barty survived a near-collapse in the second set from 5-2 to come away with a 6-1 7-6(7) victory over fellow Australian Daria Gavrilova to set up a third round match with Russian 29th seed Ekaterina Alexandrova.
An all-Italian affair saw Fabio Fognini beat Salvatore Caruso 4-6 6-2 2-6 6-3 7-6(12) which ended in a shouting match before the court supervisor was forced to intervene but neither player was willing to discuss what was said after the match.
A day after local favourite Nick Kyrgios won in five sets, the crowd at the John Cain Arena got their money's worth again as Greek Stefanos Tsitsipas beat 267th-ranked Thanasi Kokkinakis 6-7(5) 6-4 6-1 6-7(5) 6-4 in a battle lasting over 4-1/2 hours.
Tearful Kenin crumbles under pressure of title defence
Nadal unfazed by Mmoh, unruly fan at Australian Open
Omerta off court after Italian affair between Fognini and Caruso ends in heated row
Bandaged Barty wobbles before winning all-Australia clash
Tsitsipas holds off Kokkinakis to win Greek epic
Pliskova exacts revenge on Collins as familiar foe awaits
Svitolina sees off Coco challenge to reach third round
Kyrgios gets chance to prove he's a contender not just a critic
Evergreen Lopez puts age to the test at Australian Open
Kanepi fights off nerves to crush Kenin
Spain's next big thing Alcaraz bows out on second round
Giant-killer Hsieh savouring happy hunting ground
Quotes from day four of the Australian Open
Highlights of day four of the Australian Open tennis championships at Melbourne Park on Thursday. Times local (GMT +11):
2337 NADAL EASES INTO ROUND THREE
Spanish second seed Rafa Nadal, aiming for a record 21st Grand Slam title, sealed a comfortable 6-1 6-4 6-2 win over American qualifier Michael Mmoh.
2311 BIRTHDAY BOY MEDVEDEV WINS IN STRAIGHT SETS
Russian fourth seed Daniil Medvedev celebrated his 25th birthday with a 6-2 7-5 6-1 win over Spaniard Roberto Carballes Baena. He next faces Serbian 28th seed Filip Krajinovic.
2140 SVITOLINA EASES PAST GAUFF
Ukraine's fifth seed Elina Svitolina produced a clinical display to beat American teenager Coco Gauff 6-4 6-3.
2125 DE MINAUR CRUISES INTO ROUND THREE
Home favourite Alex de Minaur struck 30 winners en route a dominant 6-3 6-3 7-5 victory over Uruguay's Pablo Cuevas.
2120 FOGNINI OUTLASTS CARUSO IN ALL-ITALIAN CLASH
Italy's 16th seed Fabio Fognini needed almost four hours to find a way past Salvatore Caruso, defeating his compatriot 4-6 6-2 2-6 6-3 7-6(12) on John Cain Arena court to reach the third round for a fourth straight year.
1927 TSITSIPAS WINS IN FIVE-SET THRILLER
Greek fifth seed Stefanos Tsitsipas survived a huge scare to beat Australian wild card Thanasi Kokkinakis 6-7(5) 6-4 6-1 6-7(5) 6-4 in a thriller lasting four hours and 32 minutes.
1823 BERRETTINI SETS UP KHACHANOV CLASH
Italian ninth seed Matteo Berrettini beat Czech qualifier Tomas Machac 6-3 6-2 4-6 6-3 to set up a third-round meeting with Russian 19th seed Karen Khachanov.
1810 CORIC CRASHES OUT
Croatian 22nd seed Borna Coric crashed out following a 6-4 6-2 4-6 6-4 defeat to American Mackenzie McDonald.
1652 KONTAVEIT SURVIVES WATSON TEST
Estonian 21st seed Anett Kontaveit recovered from a shaky start to beat Britain's Heather Watson 6-7(5) 6-4 6-2 and set up a third-round meeting with American Shelby Rogers.
1515 KENIN CRASHES OUT
Defending champion Sofia Kenin slumped to a shock 6-3 6-2 defeat by world number 65 Kaia Kanepi on Margaret Court Arena.
Kanepi next faces Croatian 28th seed Donna Vekic, who beat Argentina's Nadia Podoroska 6-2 6-2.
1515 KHACHANOV MARCHES INTO THIRD ROUND
Russia's Karen Khachanov, seeded 19th, eased into the third round with a 6-2 6-4 6-4 victory over Lithuania's Ricardas Berankis.
1455 LOPEZ GRINDS DOWN SONEGO
Spain's Feliciano Lopez, playing in his 75th consecutive Grand Slam, rallied from two sets down to beat Italy's 31st seed Lorenzo Sonego 5-7 3-6 6-3 7-5 6-4 in three hours and 18 minutes.
1435 BARTY POWERS PAST GAVRILOVA
Top seed Ash Barty fired down seven aces and racked up 20 winners in a 6-1 7-6(7) victory over fellow Australian Daria Gavrilova.
The world number one next faces Russian 29th seed Ekaterina Alexandrova, who beat Czech Barbora Krejcikova 6-3 7-6(4).
1425 RUBLEV RACES INTO THIRD ROUND
Russia's seventh seed Andrey Rublev extended his winning run to six matches in 2021 with a comfortable 6-4 6-4 7-6(8) victory over Brazil's Thiago Monteiro.
1355 BENCIC PASSES KUZNETSOVA TEST
Switzerland's 11th seed Belinda Bencic needed five match points to put away two-time Grand Slam champion Svetlana Kuznetsova 7-5 2-6 6-4.
Bencic next faces Belgian 18th seed Elise Mertens, who beat China's Zhu Lin 7-6(8) 6-1.
1240 PLISKOVA SAILS PAST COLLINS
Sixth seed Karolina Pliskova, who reached the semi-finals at Melbourne Park two years ago, booked a place in the third round with a 7-5 6-2 victory over American Danielle Collins.
Czech Pliskova next faces her namesake and compatriot Karolina Muchova, who beat Germany's Mona Barthel 6-4 6-1.
1107 PLAY GETS UNDERWAY
Play began on a hot and gusty morning at Melbourne Park with the temperature pushing 30 degrees Celsius.
Authorities reported no new locally acquired cases of COVID-19 in the state of Victoria on Thursday.
(Reporting by Ian Ransom, Hardik Vyas, Manasi Pathak and Rohith Nair; Editing by Shri Navaratnam/Richard Pullin/Ken Ferris)