The story of love triangle had potential, but the director's lack of understanding of tennis ruined the movie. First, grand slams are extremely hard to win and almost all of them have been won by the Big 3 in tennis in the last 20 years. As such, it was hard to buy into this universe where someone other than the Big 3 won 6 grand slams. Even putting that issue aside, anyone who wins multiple grand slams would be considered as having had a very successful career. There should be no criticism that the person hadn't lived up to his/her potential. Also, someone who has won grand slams 6 times has proven to know how to be the best in the world over and over. Art wouldn't need any more motivation or confidence boost from Tashi. He already knows how to win. It's reasonable that by this point of his career, all Art wants was unconditional love and support from his wife, yet Tashi couldn't even give him that. If the story had been changed to Art having won multiple ATP championships but never a grand slam, then it would've made more sense. It would've also made the characters more sympathetic as the tennis world is full of professionals with potential that failed to win a grand slam.