Rafael Nadal helped Spain to a 2-0 lead over France in their Davis Cup semi-final but was angry about the tie coming so soon after the US Open final.
Nadal lost to Novak Djokovic in an epic contest in New York on Monday but beat Richard Gasquet in straight sets before David Ferrer defeated Gilles Simon.
Nadal said: "It is unacceptable that two big events like a Grand Slam and a Davis Cup semi-final are so close."
In the other semi-final, Argentina also lead defending champions Serbia 2-0.
“If this continues, the best players in the world will stop playing in this competition”
David Nalbandian and Juan Martin del Potro established the commanding margin with wins over Victor Troicki and Janko Tipsarevic in Belgrade.
Troicki replaced Djokovic, who withdrew from the first singles rubber with a back problem, but the world number 16 was no match for Nalbandian who won 6-4 4-6 6-2 6-3.
Former US Open champion Del Potro then dismissed Tipsarevic 7-5 6-3 6-4 to put the South Americans on course for the final.
"Djokovic's absence helped us for sure," Nalbandian said. "I found out some 25-30 minutes before the match that he will not play, but I was prepared to play either him or Troicki, it did not matter."
At Cordoba's bullring, Nadal made light work of Gasquet - beating his opponent 6-3 6-0 6-1 in baking conditions - but said leading players could strike if the tennis calendar was not changed to give them more rest periods.
"I rule out nothing," said Nadal. "I wouldn't like to go as far as a strike because playing is what I like to do. But something has to happen.
"As the International Tennis Federation doesn't want to listen, it would seem that the only way to get things moving is to act in the strongest manner."
The world number two added: "If this continues, the best players in the world will stop playing in this competition."
Nadal will rest on Saturday giving Feliciano Lopez and Fernando Verdasco the chance to clinch victory by beating Michael Llodra and Jo-Wilfried Tsonga in the doubles.
If Spain triumph, it will be the third time in four years that they have reached the Davis Cup final, and will go some way to avenging their semi-final defeat by France last year.
In Sydney, Roger Federer made a sluggish start before beating Lleyton Hewitt 5-7 7-6 6-2 6-3 to move Switzerland level at 1-1 against Australia in a World Group play-off.
Federer said he was feeling the effects of his five-set loss to Djokovic in the US Open semi-finals and felt uncomfortable on an "old school" grass court.
"I all of a sudden realised this was much more difficult than I expected," Federer said.
Bernard Tomic earlier beat Stanislas Wawrinka 4-6 6-4 6-3 6-3 to give Australia a 1-0 lead.