Cahill took to his verified Facebook page on Wednesday afternoon to make the disclosure in an emotional statement.
Manchester United came from behind twice to hammer Aston Villa 4-2 at Old Trafford.
The former Arsenal manager, who newly took over from sacked Steve Gerrard, led Villa to their first home victory against United since 1995.
Brighton hammered Chelsea 4-1 at the Falmer Stadium to give The Blues their first loss since the appointment of Graham Potter in September.
The new manager replaces Steven Gerrard, who was sacked last week.
Taiwo Awoniyi’s Nottingham Forest lost 3-2 to Fulham at home as League woes continued.
The Spanish gaffer won the award beating Antonio Conte of Tottenham, Manchester City’s Pep Guardiola, ex-Brighton and now Chelse coach Graham Potter and Fulham’s Marco Silva.
Gabriel Jesus continued his blistering start to life at the Emirates with another goal on the 30th minute.
“It’s a great three points. The Premier League is tough at the moment,” West Ham manager David Moyes said after the game.
Aston Villa bounced back from last week’s first match of the season defeat to beat Everton 2-1 in the English Premier League on Saturday.
