Dusseldorf - Top seed Janko Tipsarevic suffered a 7-6 (7-1), 6-1 loss to Argentine Guido Pella to exit the PowerHorse Open in an opening match shock, with the world number ten Serb now concerned about his lack of form heading into the French Open.
With Roland Garros starting on Sunday, there is no time to lose for Tipsarevic, who has prided himself on solid play in Germany during previous appearances at the Rochusclub, venue for the former World Team Cup.
Tipsarevic won the last team title for Serbia in 2012 before the competition was dissolved, but could not seem to find his former magic on the German clay.
"I practised really good and came here early. But something happens when the match starts - I'm not the same guy that I am during practise.
"I'm really worried going into the French, I'm playing my worst tennis of the past three years. I'm really concerned with the current situation. I wanted to have a good tournament going into Paris as one of the top seeds, but now I don't know what to say."
Tipsarevic, who is struggling with Swiss Stanislas Wawrinka for the tenth ATP position, lost serve four times against 101st-ranked qualifier Pella.
The Serb went down to defeat in 89 minutes to end his spring clay season with two wins and five losses. He stands 11-11 on the season after winning a fourth career title in January in Chennai.
Pella reached his first ATP-level quarter-final as he beat a top 10 opponent for the first time to notch his fourth win of the season at the elite level.
Fellow Argentine and wild card entry Juan Monaco, the third seed, started after a bye with a defeat of Brazilian Andre Ghem 6-4, 6-4 while German Tobias Kamke booked a home win over Slovenian Aljaz Bedene 6-1, 6-4.
Results from the fourth day of the Dusseldorf ATP tournament (x denotes seeding):
Guido Pella (ARG) bt Janko Tipsarevic (SRB x1) 7-6 (7/1), 6-1
Viktor Troicki (SRB x7) bt Grega Zemlja (SLO) 6-3, 7-6 (7/3)
Juan Monaco (ARG x3) bt Andre Ghem (BRA) 6-4, 6-4
Tobias Kamke (GER) bt Aljaz Bedene (SLO) 6-1, 6-4
Jan Hajek (CZE) bt Daniel Brands (GER) 6-1, 6-0
Igor Sijsling (NED) bt Philipp Kohlschreiber (GER x4) 3-6, 6-3, 6-4
Jarkko Nieminen (FIN x6) bt Roberto Bautista (ESP) 6-4, 5-7, 6-3
Tommy Haas (GER x2) bt Ivan Dodig (CRO) 3-6, 6-4, 7-5