WIMBLEDON, England – When Jonas Bjorkman was asked to practice with a young talent from Switzerland several years ago, he wondered what all the fuss was about. The boy was 16 or 17 at the time, and hardly gave it his best on the court. Bjorkman was perplexed.

“[I] thought, Jesus, what is this kid?” Bjorkman said. “Not really ready. I thought he would take the opportunity to practice with me and enjoy it.”

Much to the surprise of everyone at Wimbledon, Bjorkman will meet up with that junior again tomorrow, this time in the Wimbledon semifinals. His name? Roger Federer, of course, the best tennis player in the world and now a close friend of Bjorkman’s. After defeating Radek Stepanek 7-6(3), 4-6, 6-7(5), 7-6(7), 6-4 in four hours yesterday, Bjorkman could think of nothing better than spending an afternoon with the top seed in the second Grand Slam semifinal of his career (the first came at the 1997 U.S. Open).

“It’s a dream come true,” the 34-year-old Swede said. “He’s just the perfect no. 1 we can have I think both on the court and off the court.”

For Bjorkman, the chance to play Federer did not come easily, even though he found himself in a favorable section of the draw.Two of his matches had already gone five sets before yesterday, and he spent more hours on court playing doubles with Max Mirnyi (they are seeded second and scheduled to play today in the quarterfinals) and mixed doubles as well (he and Lisa Raymond are in the third round).

Against Stepanek, Bjorkman varied tactics, serving and volleying, rallying from the baseline, and chipping away at a man whose serve is as large as his capacity for errors (he made 56 in the match). Bjorkman saved a match point in the fourth set tiebreaker, approaching and watching Stepanek fire a backhand into the net. He set up his own match point with a beautiful forehand passing shot down the line,and when his last serve did not come back, he repeatedly wrapped his arms around himself as if to hug the crowd. He then danced off court.The veteran has missed one of 52 Grand Slam singles events since his first at the 1993 U.S. Open, and that was for the birth of his son. This one is the sweetest of them all.

“I didn’t really believe I had any semifinals left in me,” Bjorkman said. Asked how he had done it, he paused for a moment. “It’s a good question. A lot of Advil.”

Bjorkman might need prescription painkillers against the 24-year-old Federer, who methodically turned out another marvelous match yesterday against Mario Ancic, 6-4, 6-4, 6-4.

Federer faced the most difficult draw of his Grand Slam career at this Wimbledon,and one could have forgiven him for arriving in London with a little less confidence than usual after his lackluster performance at the French Open final. Yet with two matches between him and his fourth straight title here, Federer looks more formidable on the lawns than ever. He has not dropped a set, lost his serve twice, and generally wreaked havoc on his opponents.

Yesterday, he executed all manner of passing shots, swinging volleys, and running, wrist-flick dippers in a match that might as well have been a love, love, and love drubbing. The 22-year-old Ancic has the power and panache to make most players buckle, but he could not land more than a glancing blow on Federer. Not even two rain delays could disrupt the world no. 1’s magic act.

“Usually rain delays, they slow you down,” Federer said. “I played even better. I was very, very pleased. It was an incredible performance.”

Ancic, the last man to beat Federer on grass (46 matches and four years ago), said he would be shocked if he did not retain that distinction for at least another year.

“I did some unbelievable shots,” Ancic said. “I did exactly what I have to, and then I was getting passed or I was getting some winners from nowhere.”

Let us recount a few. After the first rain delay, Ancic served at 2-2 and fell behind 0-30 after Federer smacked a backhand winner down the line. He broke with a forehand down the line as Ancic stood helplessly at net. In the opening game of the second set, Federer struck a low return, but Ancic recovered with a fine half volley deep to Federer’s forehand corner. Federer took a few small steps and whipped the ball crosscourt for a passing shot and a break of serve. And when Federer led 4-3 in the third set but faced a break point, he punished Ancic for approaching late on an ordinary forehand. The 6-foot-5-inch Croat was left talking to himself as the ball went whistling past.

For Ancic, the frustration was unending. In 41 chances at the net, he won just 17 points. Federer hit 35 winners and made 17 errors. He served seven aces and held Ancic, who had led the field with 78 aces in his first four matches, to seven.

While Federer’s progress has surprised no one,the third man to reach the final four yesterday was an unlikely candidate when the tournament began (the fourth semifinalist will be decided today, when Rafael Nadal and Jarkko Nieminen begin a match that was rescheduled owing to rain delays). Unlikely, but very welcome. Twenty-one-year-old Marcos Baghdatis plays some of the most exciting tennis on tour, and he seems to have found his game – and his confidence – on grass, despite having played only two matches on it before last month.

Baghdatis is a quick study, and has gone from nearly losing to a wild card in the first round (he vomited during the five-set match) to defeating one of the best grass-court players in the world, Lleyton Hewitt, 6-1,5-7,7-6(5),6-2.The Cypriot who wowed the tennis world with his run to the finals at the Australian Open scorched his service returns and kept the uncharacteristically uneven Hewitt, a former champion here, on his heels with flat drives and sharp angles. He said he felt pleased to regain his form after a few rough patches since Melbourne.

“I had some doubts in the middle of the year, some small injuries,” he said.

Baghdatis did not lack for confidence at important moments yesterday, winning all seven of his break points. He also served quite well, making more than 70% of his first serves in the first and fourth sets, far above his normal rate (usually around 55%). And despite a hiccup in the second set, when he lost a two-break lead, Baghdatis calmed his nerves with time to spare.

Could the fast-moving, hard-hitting Cypriot possibly win Wimbledon, no doubt causing his nervous mother to faint in the stands? Hewitt gave him a shot at the final, but no more.

“I think Roger Federer’s gonna win it,” Hewitt said. It’s hard to argue with the Australian on that one.

tperrotta@nysun.com