His sessions focused on several skills including holding breath underwater for a longer period, swimming without tiring, undertaking rescue operations without panicking and so on.
Sajan, the first-ever Indian swimmer to breach the 'A' standard time for the Olympics, had suffered a slipped disc in 2019.
McKeon then became the first female swimmer of any nationality to win seven medals at a Games when she swam the butterfly leg in the medley relay.
Sajan has made it clear that he will bounce back from the setback and vowed to work hard.
Australia's sensational run continued with Kaylee McKeown winning the 200m backstroke for their seventh gold in the pool.
Team China clocked seven minutes and 40.33 seconds, 1.17 faster than the previous record of 7:41.50 held by the Australians.
Keralite Sajan clocked 53.45s to finish second behind Abeku Jackson of Ghana (53.39s) in his heat in in 100m butterfly.
The 23-year-old, who finished runner-up to Canada's Margaret MacNeil in the 100m, touched the wall in 2:03.86, well ahead of the US pair Regan Smith and Hali Flickinger, to win China's first swimming gold of the Games.
After a disappointing fifth-place finish in 200m freestyle, Ledecky clinches the inaugural 1,500m freestyle gold in swimming.
The Keralite clocked 1:57.22s as opposed to his personal best of 1:56.38 in 200m butterfly.