Network Ten in Australia as a regular host for the network's nightly sports wrap, Sports Tonight. He also covered other two other sports for the Australian network: sailing, hosting coverage of the Sydney to Hobart Yacht Race, and golf, which he covered for five years. In 2011 alone, he covered no fewer than sixteen individual divisions of motorsport on Speed. 2013–present: NBC Sports Motorsports Formula One and IndyCar In November 2012, NBC Sports announced that Diffey would join its network to become the play-by-play announcer for its broadcasts of both Formula One and IndyCar events starting in 2013. Diffey called the day of the announcement "one of the best days of my life. People have been so complimentary." The announcement named David Hobbs and Steve Matchett as the analysts who would work alongside him for the Formula One broadcasts. In December 2015, Diffey, Hobbs and Matchett were given an Honorable Mention in a list of Best Broadcast Teams of the year published on the Sports Illustrated website SI.com. On two occasions, Diffey covered both series on the same day. On 23 August 2015, he called the Belgian Grand Prix from NBC's base in Stamford, Connecticut, before he and Matchett traveled to Pocono Raceway for the ABC Supply 500. Likewise, on 3 September 2017, Diffey called the Italian Grand Prix in Connecticut and then traveled to Watkins Glen International for the IndyCar Grand Prix at The Glen. Diffey's open-wheel focus shifted solely to IndyCar in 2018 when the US Formula One television rights were transferred to ESPN. NASCAR Diffey was one of several recurring co-hosts of NASCAR America, a weekday NBCSN program dedicated to NASCAR. While he had covered NASCAR practice and qualifying sessions with Speed, it was not until his tenure with NBC that he made his NASCAR debut as a play-by-play announcer for a race, covering the Xfinity Series (NXS) at Mid-Ohio Sports Car Course on 15 August 2015. After calling the race, Diffey spoke of the experience as "a thrill...I've been a NASCAR fan and dabbled in it, and for that to be my first race was something else." He also commentated the Richmond, Dover, and Kansas NXS races. Diffey made his Sprint Cup Series broadcasting debut alongside Dale Jarrett at Homestead-Miami Speedway in 2015, leading NBCSN's "Hot Pass" coverage of NASCAR's championship race, which focused solely on the four drivers still eligible for the series championship. Diffey