Rafael Nadal hit out at the ATP over the state of the balls, despite booking his place in the Brazil Open quarter-finals with a comfortable victory over home hope Joao Souza.
The Spaniard, who made his comeback from injury and illness last week, needed only 79 minutes and a break of serve in each set to get past his Brazilian opponent, ranked 140th in the world.
The 6-3 6-4 win eased concerns over Nadal's fitness. The 26-year-old took the decision to pull out of a doubles match scheduled for Wednesday because he wanted to rest his fragile knee. He chose to prioritise the singles tournament in Sao Paulo.
Nadal, who reached both the singles and doubles finals on his return at the Chile Open last week, will meet world number 78 Carlos Berlocq in the last eight.
"It was an important victory for me. The conditions are very difficult. The problem is not the court. The problem is the ball which is very bad," said Nadal to tennis betting news reporters
"It's the fault of the ATP for allowing play with a ball of poor quality. The ATP does not have the capacity or the infrastructure to be able to analyse the conditions before the tournament begins."
These are still very early days for Nadal on his way back to the top of men's tennis. He missed two Grand Slams during his seven-month lay-off and returned to action as low as fifth in the world rankings.
The former world number one has vowed to take things slowly as he works his way back to full fitness. In one of his regular updates, Nadal revealed his knee is not causing him any problems.
"Today, it was acceptable, normal. Let's hope it will be the same tomorrow. The important thing is that it does not hurt," he said on Thursday.
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