Nadal had not played a competitive match since pulling out of his Wimbledon semi-final against Kyrgios due to injury in early July.
Rafa Nadal was not too downhearted by defeat at the Cincinnati Open on Wednesday after the Spaniard lost 7-6(9) 4-6 6-3 to Borna Coric on his return from a six-week injury layoff.
Nadal, who will aim for a record-extending 23rd Gram Slam title at the US Open, had not played a competitive match since pulling out of his Wimbledon semi-final against Nick Kyrgios due to an abdominal injury in early July.
The 36-year-old also withdrew from last week's ATP Masters event in Montreal due to the issue but did not seem hampered by it against former world number 12 Coric, and instead put his defeat down to a lack of time on court.
"Obviously I didn't play my best match, something that can happen," Nadal told reporters. "So coming back from a tough period of time, something that's easy to accept and easy to say congrats to Borna that he played better.
"I need to improve. I need to practise. I need to return better. I need days, and that's the truth. It's obvious that I was not ready enough to win the match today.
"(It) has been a difficult injury to manage. The last month and a half haven't been easy."
"I am positive"
Flushing Meadows has been a happy hunting ground for Nadal, who has won the US Open four times, the last title coming in 2019.
He will undergo tests to confirm everything is fine with the injury, which he said still created doubt in his mind during his service motion.
"I am positive," he said. "In terms of practice, I need to start to be in a Grand Slam mode, practising the way that I need to practise to be competitive since the beginning there, and I hope I will be able to make that happen.
"I need to move forward and just start to think about the energy that the crowd gives me in New York. I know it's a very special place for me, and I enjoy it, unforgettable moments there, and I'm going to try my very best every single day to be ready for that."
The US Open starts on August 29.
READ MORE: Nadal ready for Roland Garros despite injury