Sofia, Bulgaria, 7 February 2019 | Reuters/Tennis Australia

Matt Ebden has been knocked out of the Sofia Open in Bulgaria, losing his second-round encounter to Spanish fourth seed Roberto Bautista Agut.

The Australian won the first set before the Spanish world No.19 fought back to win 3-6 6-3 6-2 in one hour and 52 minutes.

It continues Agut’s solid run of form to start the season after making a run to the Australian Open quarterfinals last month.

Russian top seed Karen Khachanov suffered a shock 6-7(6) 6-3 6-4 defeat by unheralded Italian Matteo Berrettini.

The 22-year-old Khachanov was in devastating form at the start as he dropped only two points in his first four service games.

After bagging the first set tiebreak, he then unexpectedly lost his way.

The 53rd-ranked Berrettini fired down nine aces en route to booking a place in the quarterfinals.

Sixth seed Fernando Verdasco set up a second-round showdown with Romanian Marius Copil, who outclassed Swiss Stan Wawrinka in the opening round.

Verdasco secured a comfortable 6-2 6-1 victory over Bulgarian qualifier Alexandar Lazarov.

Hungarian Marton Fucsovics upset Italian eighth seed Andreas Seppi 6-2 7-6(2) in a first-round tussle.

Defending champion Mirza Basic was beaten by Slovakian big-hitter Martin Klizan in another first-round match.

World No.38 Klizan clinched a 6-0 3-6 6-2 victory over the 27-year-old Bosnian, who lifted the trophy in Armeets Arena last year as a qualifier, winning seven matches in a week.