Speaking to reporters in Sydney after Spain's 2-1 loss to Serbia in the ATP Cup Final on Sunday evening, the 19-time Grand Slam winner appeared frustrated with the scheduling of the new 24-nation round robin tournament, reports Xinhua news agency.
"It is a long competition. Is a tough way to start the season," Nadal said."I think it's confusing for the spectators, and we need to be clear in our sport."
Recently sealing victory for Spain at the 18-nation Davis Cup competition in Madrid in November, the 33-year-old voiced his concern about having two similar tournaments back-to-back.
"I think it is a great competition (the ATP Cup), but at the same time I can't change my mind that two World Cups in one month is not real. So it is not possible," he said.
"We need to find a way to fix it and we need to find a way to make a big deal with the International Tennis Federation (ITP) and Association of Tennis Professionals (ATP) to create a big World Team Cup competition, not two World Cups in one month."
"For the health of our sport and for the benefit of our sport it is, in my opinion, it's mandatory that we fix it."
Nadal will now travel to Melbourne to prepare for the Australian Open which starts on January 20.
( With inputs from IANS )