Rafael Nadal has repeated his criticism of the 25-second rule between points after being served with a warning for taking too long between points for the second day in a row.
The world number five eased into the quarter-finals of the Madrid Masters with a 6-2, 6-3 win over Mikhail Youzhny on Thursday.
However, Nadal was warned when facing break point on his serve early in the second set and he doesn't believe such a short period of time between points makes for a good spectacle.
"I don't feel singled out. The rules are the rules. I'm not in favour of this rule without any doubt. I don't think it's good for the spectators or the players," he said.
"The spectators love to see long points, but with this rule, the only thing they favour is that this doesn't happen because with 25 seconds, it's more difficult to recover and to have many points at this level."
Nadal has been in sensational form with five tournament wins since returning from a tendinitis injury in his right knee that forced him to miss the latter half of last season, but he insists he still isn't completely over the problem.
"Sometimes I have pain. Since the first day it has been complicated sometimes.
"I try to avoid talking about it as much as possible, to whisper it, because the results have been so good that with respect to my rivals it's not the moment to analyse how I am.
"It's just to analyse that I'm playing again. That's the most important thing. While I can, I will continue on this line, if not, if one day I have pain and if I cannot continue, well, we'll have to take some kind of decision to try and solve the problem with the knee.
"Roland Garros is far away. If I'm not able to be in a good condition for Roland Garros, well then I won't be in a good condition.
"If I cannot do it, I cannot do it. The really negative thing is to be seven months without competing, not, not being able to reach Roland Garros in full condition."
Nadal's passage towards a third title in Madrid seems to have been opened up by surprise defeats to world number one Novak Djokovic and defending champion Roger Federer in the second and third rounds respectively.
And the Spaniard believes the conditions in Madrid make it more susceptible to surprises.
"The conditions here in Madrid, they make the matches to be more equal with the conditions than perhaps we can have in Barcelona, Monte Carlo, Roland Garros.
"The simple fact of altitude, we have more speed here. The ball flies faster. When the ball flies faster there is less control, when there is less control the matches are more equal. And when the matches are more equal there is more options that anything can happen. It's a simple reflection, and it's normal that there are different winners."