Why did both teams wear black armbands on 1st day of Sydney Test?

Australia and India cricketers played the first day of the fourth Test in Sydney wearing black armbands. The Australian cricketers were wearing theirs in honour of former Australia batsman Bill Watson, who died recently at the age of 87. Indian cricketers wore black armbands to pay tribute to Sachin Tendulkar's childhood coach Ramakant Achrekar, who died aged 86 on Wednesday.