A Champions League final looked a million miles away when Cahill made his debut in the competition in February's 3-1 last-16 defeat at Napoli.
But the turnaround since could not have been more dramatic.
"It's been a mad season and a fantastic season for me," Cahill told the Daily Mail.
"Making a move here has obviously worked out really well.
"First to win the FA Cup and now to go into this huge game in my first six months here is really crazy."