In a boost to the organisers of Rome Masters, Roger Federer - who missed the majority of the Madrid Masters after his wife gave birth to twin boys last Tuesday - decided to play in the tournament which he has never won.
"Oh and btw ciao tutti, I just arrived in bella Italia! Looking forward to Rome," the Swiss tweeted after a mid-day arrival in the Italian capital.
Federer hit the practice courts to begin preparations for a second-round match against French journeyman Jeremy Chardy, while Nadal also arrived to prepare his bid for an eighth title at the Foro Italico.
The Spaniard will open play against talented Frenchman Gilles Simon, who beat local wild card Filippo Volandri 6-2, 6-3.
Bulgarian 12th seed Grigor Dimitrov had to stage a comeback to defeat Simon's compatriot Eduardo Roger-Vasselin 4-6, 6-3, 6-4 while the player the young Bulgarian beat in the recent Bucharest Open final Czech Lukas Rosol beat Italy's Fabio Fognini 6-3, 6-2.
The Italian 13th seed left the court to jeers from the spectators.
Dimitrov said that a reason for his sluggish start was adjusting from Madrid's altitude to sea-level in Rome.
"The first couple of matches are always tricky, adjusting to the different conditions," said Dimitrov.
"I was flat in the first set and didn't execute my chances.
"I had to fight, but in the third set I rose a level. My racquet was slipping out of my hand at times, but I found a way around it."
The Bulgarian said that he asked repeatedly for a plain while towel which would absorb sweat on his hands but only inefficient new coloured ones were said to be available.
He next plays Croatian Ivo Karlovic, who beat Spanish qualifier Pablo Carreno Busta 3-6, 6-3, 7-6 (7/4).
Nishikori, who won the Barcelona Open on clay last month, had given Nadal a real scare in the Madrid final before he finally had to call it quits at 2-6, 6-4, 3-0.
He now has a fortnight to be ready for the French Open.
However, the 24-year-old is looking ahead with confidence to Paris after his breakthrough win in terms of the clay surface in Barcelona and confirmed that in Madrid.
"It's going to be very exciting at the French because I've never felt like this on clay. I'm very confident of whatever I hit," he said.
In the women's tournament, 11th seed Ana Ivanovic beginning with a 6-1, 6-1 rout of unseeded Italian Karin Knapp.
Australian Samantha Stosur upset 15th-seeded Wimbledon finalist Sabine Lisicki 6-3, 6-3 while American 16th seed Sloane Stephens defeated Serb Bojana Jovanovski 3-6, 6-3, 6-3.
Italy's former French Open champion Francesca Schiavone, beat Canadian Eugenie Bouchard 6-4, 6-2 with 31 winners against the Australian Open semi-finalist.