India's Rohan Bopanna will become the oldest No 1 in men's doubles history after reaching the Australian Open semifinals on Wednesday at the age of 43.
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Bopanna, who attributes his longevity to yoga, turned professional more than two decades ago and his previous highest ranking was third, which he reached in 2013.
Wednesday's win for Bopanna and Australian partner Matthew Ebden against Argentine pair Maximo Gonzalez and Andres Molteni guarantees Bopanna will be top of the new rankings when they are published on Monday.
"If a 40-plus-year-old can do this, that is an inspiration," said Bopanna.
"As a tennis player sometimes you think that the journey is done. I stuck to my instincts and believed in myself."
Bopanna said his long career had taken its toll on his body and left him with "no cartilage" in his knees.
But he said his regular yoga workouts had helped him achieve the mental and physical strength necessary to keep competing at the top level.
"Every single morning I do a lot of yoga, a lot of meditation," he said. "My mind doesn't feel rushed."
Bopanna's only Grand Slam win so far has been at Roland Garros in 2017 in mixed doubles, with Canada's Gabriela Dabrowski.
The previous oldest men's doubles No 1 was US player Mike Bryan, who was 41.
Roger Federer holds the record for the oldest men's singles No 1, at the age of 36, but Novak Djokovic can beat his mark this year.