Elevated to No 1 on Monday, but jet-lagged after a Davis Cup tie in South Africa prolonged by rain, Muster faces the prospect of being king for only a week after his first-round defeat in the Dubai Open by the Australian Sandon Stolle - a "lucky loser" from the qualifying.
Depending on the results of his rivals who are competing in San Jose - Pete Sampras needs to reach the final, Andre Agassi to win the event - it is possible that the Austrian will go down in history as the only player never to win a match while reigning as the world No 1.
Climbing the mountain once was difficult enough for the 28-year-old Muster, who has won all but two of his titles on clay. Repeating the feat could prove beyond him, courageous and fiercely competitive though he is.
The 25-year-old Stolle, son of Fred, the former French and United States champion and a runner-up at Wimbledon for three consecutive years in the 1960s, is ranked No 161. He was promoted to the main draw yesterday after the Czech Petr Korda withdrew after injuring his back during a doubles match.
The Australian took advantage of Muster's disoriented state, winning 6-1, 3-6, 7-6 after two hours. Although Muster made a stirring recovery from 1-4 down in the final set, Stolle won the tie-break, 7-0.
"Two many things happened in the last three or four days, and there were too many adjustments for me to make," Muster said. The Davis Cup tie in South Africa started on grass - the Austrian winning the first match of his senior career on the surface - and was then switched to an indoor hard court because of rain.
The tie did not finish until Monday, and Muster left the altitude of Johannesburg on Tuesday night to play on another hard court, outdoors, at sea level here.
Muster credited Stolle for denying him the pace to build his rhythm in the opening set. The Australian also served shrewdly to Muster's backhand and fed off the returns.
The Austrian was philosophical about losing the No 1 position. "I don't mind," he said. "What the computer prints out on Monday is the reality. It's not depending on me this week any more. I don't know the results from San Jose - and I'm not going to fly there to find out.''
He added: "It's good to win a Grand Slam and be No 1, even for one day or one hour but you can't live in the past. You have to look to the future.''
Two of Muster predecessors at No 1 have also departed early from the singles, Stefan Edberg following Jim Courier by losing in the first round, 5-7, 7-6, 6-4, to David Prinosil, a 22-year-old German ranked 17 places below him at No 50.
The 30-year-old Edberg has become so disappointed with his form that he may be tempted to end his farewell year on the tour early. "That would be possible, yes, because at the end of the day you need to produce results," the former Wimbledon champion said. "Playing like this is no fun.''
This is Edberg's third event of the year and follows a first-round defeat by his old rival, Boris Becker, in straight sets in Doha and a second round loss against Jean-Philippe Fleurian in five sets in the second round of the Australian Open.
Karel Novacek, the inaugural winner in 1993, set aside his worries about drug allegations and enjoyed a successful afternoon. The Czech advanced to the second round with a 6-2, 6-4 victory against Russia's Alexander Volkov.Reuse content