Rafa Nadal says his mental stability has returned after a topsy-turvy year for the former world number one.The 29-year-old Spaniard arrived in Canada last week for the start of the North American hardcourt swing having picked up his third title of the year in Hamburg.He will now hope to build on that as he attempts to claim a fourth Rogers Cup title.”It’s always about adapting your tennis,” Nadal, beaten by lowly-ranked Dustin Brown in the second round at Wimbledon, told the ATP’s website about the challengers in store over the next few weeks leading up to the U.S. Open.Also read: Rafael Nadal beats Fabio Fognini to win Hamburg Open”There’s a different way of hitting the ball, but at the end of the day it’s tennis. Hamburg had been a positive week for me. Mentally I was stable all week, something that I wasn’t able to do very often this season,” says Nadal.Twice U.S. Open champion Nadal, seeded seven, faces a potential quarter-final in Montreal with world number four Kei Nishikori who opened his hardcourt season with the title in Washington at the weekend. “My mental powers have been up and down more. Hamburg was not the case and I’m working well,” he added.World number one Novak Djokovic is the top seed.