Murray, recipient of an invitation, did not give up his service in the game (3 break points saved), won in 1h42 min.
Thiem, above all, paid for his too many unforced errors, sixteen in the first set (against 3 for Murray), and more than thirty in total, especially in the forehand.
The 28-year-old Austrian, ex-N.3 in the world today 91st, remained away from the circuit for ten months, between last June and mid-April, injured right wrist, and battle to return to the highest level.
But he is still chasing after a first victory and has now lost his first three matches: in Belgrade against the Australian John Millman (6-3, 3-6, 6-4), in Estoril against the Frenchman Benjamin Bonzi (6-3 , 7-6) and Monday night against Murray.
His last success dates back almost a year.
Precisely on May 12 in Rome.
Murray, ex-world No.1 now 78th, continues his return post-installation of a titanium hip prosthesis in 2019. He had not played in Madrid, where he was titled twice, since five years.
"I feel very lucky to have the opportunity to play in this kind of tournament, in a full stadium and with a fantastic atmosphere", he appreciated.
In the next round, the 34-year-old Brit will face either Canadian Denis Shapovalov (16th) or Frenchman Ugo Humbert (46th).
© 2022 AFP