ST PETERSBURG, Russia -- World No. 4 Nikolay Davydenko has been fined $2,000 for not trying hard enough during his upset loss to Croatian qualifier Marin Cilic at the St. Petersburg Open on Thursday.

This is just outrageous. How does [the chair umpire] know what I was trying to do? I was so upset with the whole thing I started crying.

-- Nikolay Davydenko

"Nikolay Davydenko was fined $2,000 for lack of best effort in his second-round match against Marin Cilic," the governing body for men's tennis, ATP, said in a statement on Friday.

The top seed played near-flawless tennis in the first set against the 102nd-ranked Cilic but then started making numerous errors and committed 10 double faults in the last two sets. Cilic won 1-6, 7-5, 6-1.

He was warned by Belgian umpire Jean-Philippe Dercq in the final set for not trying hard enough.

"I double-faulted to lose a game in the third set and he gave me a warning saying I was trying to lose on purpose," Davydenko told reporters after the match.

"I was simply shocked to hear him say that. This is just outrageous. How does he know what I was trying to do? I was so upset with the whole thing I started crying."

The Russian is being investigated by the ATP after his first-round match against Argentine Martin Vassallo Arguello in Poland in August attracted irregular betting patterns.

Davydenko is scheduled to take part in next week's Paris Masters, where he is the defending champion.