Novak Djokovic and Rafael Nadal are the latest players to call into question the need to have the Davis Cup and ATP Cup on the tennis calendar, particularly with both events so close together, and suggested the two should merge.
The ATP Cup will kick off its inaugural edition on Friday, replacing a number of previous Australian Open warm-up tournaments, including the popular mixed event, the Hopman Cup.
It comes six weeks after the revamped Davis Cup, which also has countries playing each other in a round-robin format, was held in Madrid.
Canadian No 1 Denis Shapovalov said on Thursday that the two events - one run by the ATP and the other by the International Tennis Federation (ITF) - should combine.
"It's a really similar event and it's literally back-to-back from the other one, so it's a little bit of a weird sensation coming from what felt like the world championships coming to play another world championship," Shapovalov said.
"So for me I don't see why the ATP and ITF can't combine, can't come to some agreement and make just one, really unique and special tournament for everyone."
World No 2 Djokovic, who heads the ATP players' council, said he agreed with Shapovalov's comments when asked for his thoughts.
"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 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, the Davis Cup and the ATP Cup. And it's six weeks apart, so they're not really helping each other in terms of marketing, in terms of the value of the event."
Djokovic's concerns were shared by world No 1 Nadal, who also questioned the timing of the events.
"It's confusing to have two World Cups of tennis in one month. For me personally that's not the ideal situation for our sport, but that's how it works today," he said in Perth.
Asked if the two should be combined into one world championship, Nadal, who led Spain to Davis Cup victory in November, replied: "I think that tennis deserves something like this."
Djokovic's first match in the ATP Cup will be against South Africa's Kevin Anderson on Saturday, while Nadal is set to face Georgia's Nikoloz Basilashvili on the same day.
Both players continued their preparations for the new season by competing last month at the Mubadala World Tennis Championship in Abu Dhabi, where Nadal won a record fifth title. Djokovic was defeated in the semi-finals by Stefanos Tsitsipas.
