Rafael Nadal said he was lucky to be part of an era of tennis that included Roger Federer and Novak Djokovic after the Spaniard won a men’s record 21st Grand Slam title at the Australian Open to move one ahead of his two great rivals. Nadal roared back from two sets down to edge Daniil Medvedev 2-6 6-7(5) 6-4 6-4 7-5 in a classic final on Sunday, only months after fearing his glorious career might be over because of a niggling left foot injury. He then paid tribute to Federer, who missed the year’s first Grand Slam to continue his rehabilitation from knee surgery and Djokovic, who was deported…