Since retiring from the tour, Cahill has been a successful tennis coach and guided Lleyton Hewitt to become the youngest player ever ranked world no. 1. After Hewitt, Cahill coached Andre Agassi, who under Cahill became the oldest player ever to be ranked world no. 1 in May 2003. Cahill joined the Adidas Player Development Program after Agassi retired in 2006 and has worked with high-profile players, including Andy Murray, Ana Ivanovic, Fernando Verdasco, Daniela Hantuchová, Sorana Cîrstea and Simona Halep. He is also an Adidas talent scout and works with promising junior players worldwide.