There have been several areas of serious concern for Californians this week. Would the price of petrol soar even more outrageously to £1.25 a gallon? Could George W Bush correctly identify Britain's Prime Minister? And would Pete Sampras make it through the night? Sadly, the answer in Pete's case was no.

It was without doubt a bit of an imposition that hopes were so fervently pinned on Sampras's survival after the wholesale culling of the seeds and other marquee names at the Indian Wells Masters Series tournament here. When you have just opened a new £50m stadium and are faced with a men's semi-final line-up comprising an Ecuadorean, a Spaniard, a Swede and an Australian the lighting of candles for Pete's continued good health is understandable.

But the game's greatest failed to come up to snuff. Twice he had staggered in earlier rounds, only to be pulled round by an anxious, urging crowd. On Friday night, against Thomas Enqvist in the quarter-finals, playing what he himself called "very mediocre tennis" Sampras fell 6-3 3-6 6-3.

"When you are not playing well you can't keep escaping," said Sampras, who needed three sets and much vocal backing to take care of Wayne Ferreira and Byron Black to get this far. Anybody scanning the statistics of the Enqvist contest could have been forgiven for marking the score heavily in Pete's favour. He had beaten the blond Swede nine times. But, clearly, nobody beats Thomas Enqvist 10 times.

These days Sampras's hair is thinning. At 28, bare patches are suddenly visible in his game, too. No doubt he will pull himself together, as he usually does, in time to win Wimbledon yet again. But for the moment the best player of his age is vulnerable.

Sampras's only decent performance of the week had come in his opener against Andrei Medvedev at night, when he felt the cooler conditions had helped to prevent the balls flying in the desert air.

Perhaps, to be Widdecombian about it, there is something of the night about Pete, even if he does favour all-white kit. But on this night Enqvist had no need to drive a stake through his opponent's heart. Sampras took care of that chore himself.

Since losing that classic semi-final to Andre Agassi at the Australian Open in January, Sampras has played only at Scottsdale, where he took a wild card, beat Greg Rusedski and pulled out next day with a back twinge (suffered, claimed Rusedski with a touch of malice, on the golf course).

So on to Charlie Pasarell's new field of dreams, another location where he has not pulled up too many trees since winning the title in 1994 and again a year later. In fact, he won two matches in four years but felt, in his own dramatic phrase, "I was exorcising my desert demons", when he got through three rounds. On Friday, under the lights, the demons had their revenge.

Sampras's serve, the heart of his game, produced 10 aces and an equal number of double faults. In the one hour 33 minute contest he committed 43 unforced errors, almost 11 complete games thrown away. If Enqvist were the smiling sort, he would surely have worn a large grin at the end. Being a modest Swede, he refrained from overt jubilation but was visibly chuffed.

The alarm bells were clanging early. In the fifth game Sampras spurned a brace of break points but the real horror was reserved for the eighth game when he dropped serve with a volleying error and three successive double faults. That disaster seemed to have itseffect on Enqvist, too.

The 25-year-old from Stockholm wobbled as he served for the set, going break point down by pushing hopelessly wide such a simple volley that he dropped his racket in disbelief. Not to worry. A Swedish ace and an errant forehand from Sampras still left the set in his hands after 31 minutes.

The second set was only two games old when Sampras plunged into trouble again, fighting off four break points to the beseeching cries of a large audience.

That achievement did him so much good that he bounced back at once, benefited from four Enqvist forehand mistakes and broke for a 3-1 lead as he alternately scared, teased and delighted the punters, holding on to level the match at one set all after an hour and six minutes.

Still Sampras had not shaken off the worst. "Horrendous" was the description he used for the service game, containing another two double faults, which left Enqvist in the driving seat and with the finish line in sight at 4-2 in the final set. The Swede is too much of an accomplished professional to spurn such an invitation.

Sampras explained that, because his first serve was malfunctioning, he was going for big second serves and frequently missing those, too. "I was hoping my form would get better as the week went on but it just didn't happen. Thomas is a top 10 player and I needed to be sharper. You can't play two horrendous service games, you can't lose your concentration at this level." Sampras did exactly that, and paid the price.

Results from the Tennis Master Series-Indian Wells tournament, presented by Newsweek:

Men Singles Quarter-finals

Alex Corretja, Spain, def. Magnus Norman (6), Sweden, 4-6, 6-2, 6-2. Nicolas Lapentti (8), Ecuador, def. Hicham Arazi, Morocco, 6-2, 6-0. Mark Philippoussis (12), Australia, def. Sjeng Schalken, Netherlands, 7-6 (7), 6-4. Thomas Enqvist (10), Sweden, d. Pete Sampras (2), United States, 6-3, 3-6, 6-3.

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Doubles Quarter-finals

Jared Palmer and Alex O'Brien (2), United States, def. David Adams and John-Laffnie de Jager, South Africa, 6-3, 6-0. Roger Federer, Switzerland and Dominik Hrbaty, Slovakia, def. Todd Woodbridge and Mark Woodforde, Australia (3), 3-6, 6-4, 6-3. Paul Haarhuis, Netherlands and Sandon Stolle, Australia (7), def. Ellis Ferreira, South Africa and Rick Leach (1), United States, 6-7 (3), 6-4, 7-5. Wayne Ferreira, South Africa and Yvegeny Kafelnikov, Russia def. Paul Goldstein and Chris Woodruff, United States, 6-2, 6-4.