Sydney - World number one Rafael Nadal renewed his call on Sunday for the new ATP Cup to merge with the Davis Cup, urging tennis chiefs to fix it "for the health of our sport".
The inaugural 24-team ATP Cup, played in Sydney, Brisbane and Perth in a revamped start to the season, has proved a hit with many players and fans.
But it took place just six weeks after the new-look Davis Cup in Madrid, won by Nadal's Spain, which also has countries competing against each other in a round-robin format.
One of the events is run by the men's tour, the Association of Tennis Professionals, and the other by the International Tennis Federation.
Nadal, along with world number two Novak Djokovic, believe they are too close together.
"I think it (ATP Cup) is a great competition, but at the same time I can't change my mind that two World Cups in one month is not real," said Nadal after he was beaten by Djokovic in two sets during the ATP Cup final.
"It is not possible. We need to find a way to fix it and we need to find a way to make a big deal with ITF and ATP to create a big World Team Cup competition, not two World Cups.
"I think that's a confusion for the spectators, and we need to be clear in our sport," he added. "And for the health of our sport and for the benefit of our sport, in my opinion, it is mandatory that we fix it."
The issue of merging the two was first mooted by Canadian Denis Shapovalov this month and backed by Djokovic, who heads the ATP players' council.
"We need to have one Super World Cup event, whatever you want to call it," he said.
"That's not going to happen next year as well. But if the two sides, the ITF, the Davis Cup, and the ATP get together very quickly, it can happen possibly for 2022.
"I hope it will happen because it's kind of hard to get top players to commit to play both events."
Asked when would be the best time to hold a combined event, Nadal was non-committal.
"I can't tell you my real opinion, because it will not make sense today. And it's not that easy. It needs a little bit (of a) longer conversation."
But he did hint that holding such a gruelling competition at the start of the year was not ideal.
"Is a long competition. Is a tough way to start the season. I don't know."