Rafael Nadal began his comeback with a doubles loss at the Brisbane International but he has not closed the door on playing singles beyond this season.

Nadal had an operation on his left hip in June and has indicated this season will very likely be his last, but the desire to play on remains strong.

"If I am playing well - something that can happen - if I am free of injuries - something that history says is very difficult - and if I am not having too much pain on a daily basis, if all the things together happen, why not?" Nadal, 37, told BBC Sport.

"I don't want to say 100% that's going to be my last year, because I keep loving tennis and keep enjoying what I am doing."

His doubles partner in Brisbane, Lopez, is part of Nadal's coaching team and rarely plays these days, but it was useful practice before the Spaniard's singles match with 2020 US Open champion and qualifier Dominic Thiem on Tuesday.

"Competing is different than practising, but in terms of practising with the guys here, I am quite happy because I feel competitive against the players that I played in practice," said Nadal, who had not played since January's Australian Open.

"Of course I don't have the expectations that I used to have in the past."