When the world tennis rankings are updated on Monday, they will show India’s Rohan Bopanna, 43, as the world’s number one player in men’s doubles. After 21 years on tour, it’s a remarkable first for Bopanna. While he’s played his tennis at a time when the aspect of physicality in tennis has increased, it’s also been a time when players — male and female, in singles and doubles — have pushed the boundaries of longevity further.