By Andrew Holleran Rafael Nadal has done it again. The legendary left-handed has climbed back on top of the tennis world, winning the Australian Open on Sunday morning – his 21st Grand Slam championship, the most in men’s history. Nadal rallied to defeat Daniil Medvedev in the men’s final of the Australian Open on Sunday morning for another Grand Slam title. His 21 Grand Slams are the most in men’s tennis history. Legendary tennis star John McEnroe summed up his thoughts on Nadal following the big win on Sunday morning. “I’ve watched a lot of tennis and I’ve seen a lot of unbelievable champion…