Cook Does Vanishing Act, Twice : Tennis: After his game disappears in second-round upset, No. 1-seeded player is nowhere to be found.

It is lonely at the top, but Jason Cook apparently wanted to remain lonely Thursday after he was knocked off the top of the mountain.

The Woodland Hills resident, seeded No. 1 in the boys’ 18-and-under division, was upset in the second round of the Southern California Junior Sectional tournament by David White of Rancho Santa Fe.

And in the blinking of an eye, after White hit a passing forehand volley to complete a 7-5, 6-7 (8-6), 6-4 victory, Cook gathered his equipment and vanished from the Los Caballeros Sports Village.

Cook was apparently distraught after suffering only his second defeat this year. The 18-year-old bound for New Mexico on a tennis scholarship had a 26-1 record in juniors play and had been an overnight sensation in his division.

But Cook’s whereabouts were unknown even to his coach after he was bumped in the round of 16 in his most important tournament to date--a qualifier for this summer’s nationals.

“Cook will go into hibernation,” said Craig Heinberg, his coach. “He’s probably trying to kill himself. He knows I’m disappointed.”

The two top players in this tournament were Heinberg students. Both are out of it. The other was Krissy Hamilton of Agoura Hills, Heinberg’s stepdaughter. Hamilton, seeded No. 1 in girls’ 18s, had to default before the tournament, Heinberg said, because of a foot injury.

“These tournaments are brutal,” Heinberg said. “Everybody comes out swinging. They close their eyes and take their shot.

“Jason played pretty average. He played a little tentative. This other guy swung out.”

White was able to neutralize Cook, a 6-footer who plays a serve-and-volley game, at the net. And the counter-attacking style of White seemed to affect the rest of Cook’s game, including his big serve.

Leading, 5-4, and serving for the first set, Cook put a backhand volley into the net, went wide with a backhand and put a forehand into the net to give White a break.

White held serve and broke Cook again to win the set with a backhand passing shot while Cook charged to the net.

That scenario would repeat itself several times, with White crushing winners down the lines or lobbing the ball over Cook’s head.

“That was a big part, just to get it at his feet and not go for the pass right off his serve,” said White, who is ranked 10th and is 3-0 against Cook.

White had two golden opportunities to win the match in straight sets. Leading, 4-2, and serving in the second set, White saw Cook break back and force a tiebreaker.

In the tiebreaker, White led, 6-4, and twice had match point. But he hit two errant shots on his own serve and Cook added a pair of drop winners to win, 8-6.

With the third set tied at 4-4, White hit a backhand winner off a weak overhead smash by Cook to break serve and lead, 5-4. Cook looked tired and White went for the kill, serving out the match with a love game.

“The third set was back-breaking,” White said. “I just had to concentrate really, really, really hard. It kept haunting me in the third, that 6-4 in the breaker. I had to keep putting it out of my mind.”

Somewhere, Cook was in seclusion with a mind full of regret.

Last year, he had to fight through the qualifying tournament, only to lose in the first round to Derek Pope of Ojai. After that, Cook dedicated his life to tennis.

He withdrew from Calabasas High and entered a home-study program. In September, he began a regimen of weightlifting, running and six hours of practice a day.

He grew from 5 feet 9 to 6 feet, and his ranking rose from No. 13 at the end of 1994 to No. 1.

Cook steamrolled Adam Gross in Wednesday’s first round, 6-1, 6-1.

“He’s a good player but I’m just playing really well right now,” Cook said. Thursday he wasn’t.

“It’s a tough way to go,” Heinberg said, “but [Cook] will probably still be No. 1.”

Perhaps, but Cook is likely to lose that ranking if second-seeded Noah Newman of Hollywood wins the tournament.

In the boys’ 18s, Dylan Mann, 16, of Canoga Park defeated Brett Masi of Riverside, 6-4, 4-6, 6-4. No. 7 Nick Varvais of Simi Valley beat Ryan Hollis of Orange, 6-3, 7-5. At noon today, Mann plays White and Varvais faces unseeded Geoff Abrams of Newport Beach.

In girls’ 18 singles, No. 4 Mugette Ahn of Los Angeles beat Romy Mehlman of Harvard-Westlake High, 6-1, 6-0. No. 3 Amanda Augustus of Palos Verdes Estates defeated Monique Allegre of Camarillo, 7-6, 6-2. Kristina Kraszewski of Torrance beat No. 5 Brandi Braverman of Studio City, 7-6, 6-0.