Novak Djokovic criticised the packed ATP calendar on Saturday after a second withdrawal of an opponent helped him reach the final of the Rome Masters.
Radek Stepanek pulled out from his semi-final with the world number three 24 hours after Nicolas Almagro retired against the Serb in the last eight.
Andy Roddick also had to quit early in the other semi-final against Stanislas Wawrinka with a back injury.
Djokovic said: "The players are not getting injured for nothing."
A tournament which has been dogged by injuries also saw Almagro awarded a walkover to the quarter-finals after Chilean Fernando Gonzalez, last year's runner-up, pulled out of their third-round match with a leg injury.
The controversial withdrawals will no doubt provoke more debate, sparked by world number two Rafael Nadal on Wednesday, on whether the increasingly-crowded tour schedule is putting too much of a strain on the top players.
The 2008 clay court season has been squeezed due to American television scheduling requirements with the US spring hard court season finishing a week later because of the NCAA basketball championships.
Rome was preceded by successive clay tournaments at Monte Carlo, Barcelona and Munich and will be followed next week by Hamburg before the game's top stars head to Paris for the second major of the season, the French Open starting on 25 May.
And Australian Open winner Djokovic admitted: "The players at the top and the ones who are playing a lot of matches are not happy with the schedule this year.
606: DEBATE
"We are well aware of the fact that the Olympics are making it even more difficult, but this is something that we will need to talk about in the future.
"I'm not criticising anyone, but it's very important to take care of the players.
"We don't want to have these kinds of situations at big events, the players retiring in the semi-finals and quarter-finals after one set.
Djokovic's comments echoed those of world number two Rafael Nadal, who called the calendar "impossible" on Wednesday after playing with a foot problem during his shock second round defeat by fellow Spaniard Juan Carlos Ferrero.
American sixth seed Roddick believed it was probably a coincidence that so many players had been injured in Rome, but agreed that the calendar needs to be lightened.
"I have been saying for years that the schedule needs to be adjusted and there needs to be a little bit more time to recover at the end of the year," he said.
The ATP issued a statement promising reforms to the calendar in 2009 that would offer players "a fairer and healthier schedule" by allowing them to plan their travel schedules more effectively.
ATP chief executive officer of Europe Andy Anson said: "Our wide ranging changes to the existing season, combined with a new Davis Cup schedule, will ensure that the unique situation of an ATP calendar that contains shortened clay and summer hard court swings is not repeated in future years."
~RS~q~RS~~RS~z~RS~15~RS~)