Fresh from his record seventh clay-court French Open victory, Rafael Nadal arrived at the pre-Wimbledon warm-up tournament at Halle, as Swiss star Roger Federer warmed up for his bid for a sixth title on the grass here.
"I'm delighted to be playing again in Halle," said Nadal, who has not played here since his first round elimination in 2005, favouring London's Queen's club to north-western Germany, ahead of his bid for a third Wimbledon title.
The world number two will take to the courts on Wednesday in doubles with fellow Spaniard Marcel Granollers, before opening his singles campaign against Slovak Lukas Lacko, who beat Russian qualifier Konstantin Kravchuk 2-6, 6-2, 6-3 in their first round tie on Tuesday.
Nadal has won his three previous meetings with the 58th-ranked Slovak but the Spaniard nevertheless dropped the second set of their clash in Doha last year 6-0.
Federer, beaten by world number one Novak Djokovic in the French Open semi-final last Friday, is bidding for his sixth Halle title with his first opponent Germany's Florian Mayer on Thursday.
Home hope Tommy Haas advanced to the second round on Tuesday after Australian Bernard Tomic withdrew citing illness while trailing the German 5-2 in the first set.
"He told me he'd been sick for the past ten days and still didn't feel well but had wanted to play," said former world number two Hass.
Tomic, ranked 27th, was eliminated in the second round of the French Open, but had been hoping to warm-up for Wimbledon here after reaching the quarter-finals last year in the All England club.
The 34-year-old Haas, the 2009 winner here, on Monday received a wild-card to play his 13th Wimbledon, and next faces Spanish sixth seed Marcel Granollers who eliminated German qualifier Misha Zverev 6-4, 6-2.
Italy's Andreas Seppi, the seventh seed, who gave Djokovic a scare in the last-16 at the French Open, fell to Czech veteran Radek Stepanek 7-6 (8/6), 4-6, 7-6 (9/7) in their first round clash.