The 33-year-old leapfrogged Novak Djokovic in the ATP Rankings on Monday to become the new world number one, after winning the French and US Opens this season.
Djokovic can still snatch back the No.1 tag if he outperforms Nadal in London, though he may not have to, if the Spaniard continues to struggle with an abdominal injury.
Nadal withdrew from his semi-final clash with Denis Shapovalov at the Paris Masters just minutes before it was due to start and there were reports that the 33-year-old would not recover in time for the final event of the season.
But the 19-time Grand Slam winner is confident he will be fit in time to face reigning champion Alexander Zverev on Monday evening.
"[I'm feeling] good, happy to be here," Nadal said. "But I don't know. I need to go day-by-day after what happened in Paris. The first thing is I'm happy to be here because I haven't been able to play, so I'm excited to play after a couple of years. I need to work every single day and I have a good hope to be 100 per cent ready for Monday.
"I started [serving] yesterday. I was playing well in Paris and my plan is to be [in] perfect [condition]. I was serving well over the last two matches so I am confident I can be competitive.
"There are many good players in the competition so I need to be 100 per cent ready. I hope I can serve every single day even better."
Having been plagued by knee problems over the past few years, Nadal has enjoyed one of his most consistent seasons in recent times.
He reached the Australian Open final - where he lost in straight sets to Djokovic - before continuing his phenomenal record at Roland Garros with a record 12th title and overcame Daniil Medvedev in a marathon five-setter to win at Flushing Meadows.
Despite a minor blip at the Barcelona Open, where he was defeated by Dominic Thiem in straight sets, Nadal revealed he has been happy with his performances in 2019.
"It's been a great season," he added. "The first few months of the season I was playing good tennis, from my side, and almost every minute I have been playing. I'm happy to have turned it around after Barcelona."
Asked what it would mean to win one of the few titles that has eluded him in his career, Nadal replied: "At first I have to play!"
"I've qualified for 15 years and I don't know how many I have gone through to complete, so I would love to have the opportunity to win it but I can't complain about all the things I have achieved.
"I will work my hardest to compete as best as I can to try to win it."