On the practice court, players draft the designs for the games they aim to build. Then there are those creative souls who blow up blueprints.

It was on a practice court at Crandon Park on Key Biscayne where Jonas Björkman hit with the teenager whose eye-popping shots dazzled like the Art Deco structures dotting South Beach, but the kid's concentration could collapse as quickly as a sand castle party crashed by marauding waves.  
Months earlier, a 17-year-old Roger Federer beat a pair of Argentine juniors named David Nalbandian and Guillermo Coria in succession to win the Orange Bowl at Crandon Park, clinching the 1998 year-end junior No. 1 ranking. "That's the best serve I've faced in the juniors," Coria said after Federer's 7-5, 6-3 victory in the final. It was a transformative moment: The Swiss teenager celebrated, adopting a bleach-blonde hair style. Federer's hair had returned to its natural shade, but his head was still in flux when Björkman encountered him at practice that spring day in 1999.  
"You could see he had such a massive game, but mentally he was pretty weak at that time," Björkman recalls. "But in one year, he developed so much. You saw him again as a 19-year-old and he was so mature and he had such a tremendous talent you knew he was going to be a phenomenal player."  
Federer celebrates his 31st birthday today — weeks after regaining the world No. 1 ranking — looking like a man fully intent on enjoying his tennis golden years.  
Perhaps the only experience as exhilarating as facing Federer in singles is partnering him in doubles. What does it feel like to play alongside an all-court improviser capable of hitting between the legs or over an opponent's head? We caught up with some of Federer's former doubles partners to find out.  
The 17-time Grand Slam singles champion has played 199 doubles matches in his pro career, partnering 27 different men and a couple of women (Martina Hingis in Hopman Cup and wife Mirka in Hopman Cup and in life). Federer teammates have ranged from Grand Slam champions (Björkman, Lleyton Hewitt, Max Mirnyi, Marat Safin, Marc Rosset) to former junior opponents (Nicolas Escude and Andreas Vinciguerra) to a slew of Swiss friends and Davis Cup teammates, including Yves Allegro, George Bastl, Marco Chiudinelli and Michel Kratochvil.  
Kratochvil, two years older than Federer, rose through the ranks with the ball boy from Basel. He recalls the young Federer as "very relaxed" both on and off the court, but says even those closest to him could not envision his evolution.  
"I think everybody knew this boy had lots of talent, but when we were young, I don't think anyone could foresee that he could become No. 1 and the best ever," says Kratochvil, who now runs the Michel Kratochvil Tennis Academy.  "I think it's a couple of key things that helped Roger reach his success. It was a lot of hard work — you cannot achieve anything without hard work — and Roger has an unbelievable talent. His whole genetic posture, the way he plays a variety of shots, the way he moves, the way he anticipates on court — it all makes him so special. And because of that style, Roger has not had very many injuries and that also gives him the possibilities to do shots that others cannot. I think those are all important reasons for his success."  
Federer was still a few years from singles success when he embraced the doubles Beast. Max Mirnyi, "the Beast of Belarus", won three titles with Federer —  Rotterdam and Moscow in 2002 and Key Biscayne in 2003 — the most titles of any Federer doubles partnership. But he wasn't exactly banking on Federer re-writing the record book back then.  
"To be honest, there was no way I could have predicted that Roger would turn into a superstar and a legend of the game back then," Mirnyi says. "He had some effective shots, but he also had some flaws to his game, as is the case with many promising young players and older, established players as well.  
"Playing with him was an absolute pleasure. Even though he was not yet a magician at the time of our partnership he already had plenty of tricks. He was starting to show us, his colleagues, the different dimension tennis could be played at."  
While he was developing an all-court game, the young Federer was vulnerable to vets who could get to his backhand, which was not nearly as polished or penetrating as the multi-faceted shot it would become. Former Top 10 singles and doubles player, South African Wayne Ferreira, partnered Federer to the 2000 Wimbledon doubles quarterfinal and points to the work Federer did reconstructing his backhand with ex-coach Peter Lundgren as vital to his development.  
"Being South African, as is Roger's mother, I knew him since he was younger and we practiced together a lot," Ferreira says. "As a teenager, he had a really good forehand and he moved extremely well. I remember early on, he had no topspin backhand — he only had the slice backhand. I beat him in singles only because I was able to hit my forehand to penetrate his backhand. So I knew from practicing with him, that Roger was very talented, but his backhand was a weakness. Working with Peter Lundgren, they realized they had to improve that shot and then he began to come over it. Once he developed the topspin backhand, he was fantastic, the full package."  
It would be overstating the case to suggest playing doubles was critical to Federer's all-court game. Certainly, doubles sharpens the serve and return through repetition and may have helped Federer refine the rough edges on the backhand and fine-tune his transition game. But some partners believe Federer, who was not above tossing his Pro Staff around in fits of frustration during his younger years, found refuge from immense expectation in singles and a relaxed state of mind playing doubles.

"I think the biggest positive playing doubles was to get away from the pressure as a youngster coming up and people saying you're gonna be the next Pete Sampras," says Björkman, with whom Federer won his first doubles title at the 2001 Rotterdam event. "Obviously, it must be pretty tough to go into every match with those expectations at such a young age. When you play doubles, it's a totally different game. It was a good way for him to get match practice and also be a little bit more relaxed on court. Hopefully, maybe he learned a bit from all of us he played with."

Mastering the mind game may have been as important as working on his net game.  
"In my opinion, there was something within Roger himself, his inner psychological world and mental approach to the game that changed from when he began," Mirnyi says. "And then that made the difference in the player that we have all had the pleasure to watch over the last 10 years."  
In the years since, Federer has returned to doubles, winning the 2008 gold in Beijing with Wawrinka and paying it forward in partnering lower-ranked Swiss players to give them experience, while several of his former doubles partners continue to follow his career, collectively sharing a similar birthday wish: That he continue playing.  
"The most impressive thing to me is the way he has handled all of his success: He is still the same person he was when I met him years ago and he knows the importance of world No. 1," Björkman says. "What's really most remarkable is that you see him winning so much for so long yet every time he wins, like at Wimbledon, you see how genuinely happy he still is and how much he loves it. I don't think we have ever had such a good ambassador in the sport of tennis."