Murray made an unhappy start to 2023 with a straight-sets defeat to Sebastian Korda at the Adelaide International on Tuesday.
Korda, who at 22 is 13 years Murray's junior, had won their only previous meeting at the 2022 Gijon Open.
The 6ft 5in American, ranked 33 in the world and 16 places higher than the British number four, repeated that victory with a 7-6 (3) 6-3 success in one hour and 56 minutes.
The first set went with serve until Korda broke in the seventh game to lead 4-3.
Three-time grand slam champion Murray broke back instantly to set up a tie-break that Korda dominated.
Korda's double break gave him a 4-1 lead and, although Murray saved one set point, the American closed out the first set in one hour and 16 minutes.
The second set followed a similar pattern with serve held until Korda took a 4-2 lead.
Murray had a break point in the next game, but he was unable to capitalise and Korda served out to secured a second-round date with Spain's Roberto Bautista Agut.
The Scot has indicated that he could drop a retirement announcement at any time if he feels his time is up.
Murray said at the Laver Cup that he wouldn't seek a farewell like Roger Federer.
"Look, I'm really not thinking about that right now," Murray said.
"I certainly won't and don't deserve to have a sendoff like that. You know, Roger did deserve that night, and it was super special having all of those guys there, you know, watching on the side of the court, and having them there made it really special.
I mean, look, for me, I'm not going to have a farewell match, I guess, like that. I probably would announce when I'm going to play my last event and stuff, but when that is, I don't know. Like, I'm still playing competitive tennis and physically feeling good against top players. I just need to start really turning some of these, you know, tight losses and close matches into wins. It's as simple as that."
Also on Tuesday in Adelaide, Novak Djokovic started his singles season with a routine victory.
"For the first match I can't complain, I played very well," said the 35-year-old, who is now the world number five and will be seeking a record-extending 10th Australian Open men's singles title later this month.
"Thank you all for coming out today. Thank you for giving me the welcome that I could only wish for.
"If I have to pick one country where I've had the most success, which treated me in the best way in terms of tennis, it's here, definitely."