The 18-year-old Vancouver native has already played 12 lower level pro tournaments and earned a total of US$10,276, but the life of a professional begins for good at a $15,000 ITF Futures Tour event in Markham, Ont., beginning Sept. 17.
"I think I'm very ready to begin the transition in the Futures," Peliwo said Monday at the national tennis centre in Montreal. "I've already been doing it the last year and half.
"I know I can get to the top level if I keep working and stay healthy. I'm excited to see how the next few years go."
There is nothing left to prove at the junior level.
This summer he became the first Canadian male to win a Grand Slam event of any kind when he claimed the junior boys singles title at the All England Club on the same weekend that Genie Bouchard of Westmount, Que., won both the junior girls singles title and doubles crown with American partner Taylor Townsend.
Peliwo made it two in a row on Sunday when he bested England's Liam Broady in a nervy, three-set final to win the U.S. Open junior title.
That guaranteed he will be the No. 1-ranked junior for the rest of the year, which left him free to pursue his pro career full time.
"It feels good actually, now that I don't have to worry about the juniors," said Peliwo, who also reached the final of the Australian and French Open junior draws. "There are not as much expectations as there is in junior.
"I'm still the underdog. I'm ranked (609th). I can just play my game, learn as much as a I can and try to get a few wins. I'm looking forward to it."
Winning junior Grand Slams is no guarantee of success as a pro.
Past U.S. Open boys champions include Andy Murray (2004), Jo-Wilfried Tsonga (2003), Andy Roddick (2000) and David Nalbandian (1998), but just as many go on to modest careers. It is the same for Wimbledon, where past junior winners include Bjorn Borg (1972), Ivan Lendl (1978) and Roger Federer (1998).
"To be compared to those guys at all is amazing," Peliwo said. "To have gone down the same path is a great feeling."
Peliwo became the first to reach the final of all four junior Grand Slams in one year since Australian Mark Kratzmann in 1984. Kratzmann had a decent pro career, winning 18 doubles titles, before switching sports to play cricket.
The last male to win the Wimbledon and U.S. Open juniors in the same year was Grigor Dimitrov in 2008. The Bulgarian has not, as some hoped, become the next Federer. The 21-year-old is currently ranked 58th.
Louis Borfiga, who runs the Montreal tennis centre, said the five-foot-11 Peliwo has work to do to succeed as a pro, but he likes how he plays.
"It's very difficult, the transition between junior and pro, but he has a good game," he said. "His baseline is very good and he can improve a lot of things, for example his serve.
"He has a good quality of ball. Sometimes he can play very fast. I think he has a good chance for the future."
The national tennis centre has been pumping out some impressive players in recent years, including Milos Raonic, who is ranked 16th in the world. Vasek Pospisil is 103 and rising.
Adding two Grand Slam junior titles apiece from Peliwo and Bouchard is another feather in the cap.
"It's very important for us because now we have credibility, not only in Canada but around the world," said Borfiga. "Everyone's asking what's happening in Canada, and for us it's fantastic."
Peliwo said the jump he made from contender to champion in junior events came from being mentally tougher, which allowed him to keep battling when things didn't go well and to win matches even when not playing his best tennis.
His goal for the year was to win a junior Grand Slam, and he ended up with two.
"I can honestly say I didn't expect this, but it was a great finish to the year," he said. "It was exactly how I would have liked to do it.
"It's going to be a whole different story in the pros. I'll have to work on my physical strength because those guys are a lot stronger than the juniors. They're a lot bigger. I need to improve every part of my game, really. I'll try to get more power, more speed, more consistency."