Rafael Nadal begins first singles match in almost a year
The 37-year-old has not played singles since a second-round loss at the Australian Open last year, undergoing two rounds of hip surgery.
The long lay-off raised fears his career could be over, but Nadal said this week he was always determined to make it back for the 2024 season.
He conceded there was "a high percentage" that it would be his last season, but left the door open to play on should his body hold up.
The 22-time Grand Slam champion made a low-key return on Sunday in a first round doubles match alongside countryman Marc Lopez, which they lost to Australian pair Jordan Thompson and Max Purcell.
However, all the focus this week has been on his singles return after organisers granted him a wildcard, with a full house in Pat Rafter Arena to give him a loud reception when he walked on court.
Nadal will not have it all his own way against Thiem, who reached a career-high world ranking of three before suffering his own injury problems.
The two men have played 15 times, with Nadal winning nine and Thiem six.
However, the Austrian has won their past two encounters at the ATP Tour Finals in 2020 and the Australian Open the same year.
Nadal won both his opening service games to love against former US Open champion Thiem.