Ageing Andre Agassi was knocked out of the Hamburg Masters 6-2, 7-6 by unseeded Spaniard Feliciano Lopez in a first-round upset on Tuesday.
Ninth seed David Nalbandian also lost 7-6, 7-5 to promising Swede Robin Soderling but fellow Argentines Gaston Gaudio and the indefatigable Guillermo Coria won easily, as did Russian Marat Safin.
Lopez, ranked 26th in the world, outplayed 35-year-old Agassi in cold conditions on the slow clay of the Rothenbaum centre court.
The eighth seed looked sluggish in the first set and tossed away a 4-2 lead in the second before Lopez sealed victory on his fourth match point, taking the tiebreak 7-5 with a forehand volley.
"They were tough, tough conditions out there," a dejected Agassi told reporters.
"It's too hard for me to move in those conditions. I wasn't penetrating and I wasn't reacting very well. It was a difficult day."
The former world number one has been in good form this season but his defeat meant he joined fellow American Andy Roddick among several seeds to go out early at the pre-French Open event.
Second seed Roddick lost in three sets to Chile's Nicolas Massu on Monday and he too said the cold conditions had been a big factor.
Temperatures in Hamburg have been struggling to reach 10 degrees Celsius this week.
Lopez described his triumph over Agassi as "one of my best wins ever".
French Open champion Gaudio, seeded four, brushed aside Spain's David Sanchez 6-2 6-2, making light of the unpredictable weather on court one in a sparkling display less than two weeks before the claycourt grand slam in Paris.
He now meets 2002 French Open champion Albert Costa of Spain.
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Coria, the 10th seed, thrashed American Vince Spadea 6-0, 6-2, showing no sign of tiredness after his five-hour defeat by Spanish teenager Rafael Nadal in the Rome Masters final on Sunday.
Russian third seed Safin, the Australian Open champion, signalled a return to form by making quick work of his Spanish opponent, Alberto Martin, in the evening match.
Safin won 6-1, 6-0 to set up an enticing second-round match against 2003 French Open champion Juan Carlos Ferrero of Spain.
Czech teenager Tomas Berdych beat Spain's David Ferrer 6-2, 2-6, 6-3 and will tackle top seed and world number one Roger Federer, the player he beat in a major surprise at last year's Athens Olympics.
Federer is in the same quarter of the draw as 2004 French Open runner-up Coria, who lost to the Swiss in last year's Hamburg final.
Thailand's Paradorn Srichaphan looked out of sorts in a limp 6-2, 6-3 defeat by Czech Jiri Novak while Germans Rainer Schuettler and Tommy Haas lost on centre court to the disappointment of home fans.