His All Australian brother, Chad Cornes, also attended Sacred Heart College and played for Glenelg in the SANFL.

He was also the leading possession winner in the AFL, received the most Brownlow votes for the year for Port Adelaide, and won their best and fairest, the John Cahill Medal, ahead of brother Chad.

Instrumental in the Power's late season fortunes, his third best and fairest highlighted his durability as a mainstay of the Port Adelaide engine room.

[1] Playing more on the wing and across halfback, he was sent back to Glenelg in the SANFL with a view to adapting better to the coaching panel's new expectations.

Cornes received high praise for returning to his acclaimed tagging football with top performances on midfield heavyweights Brent Harvey (North Melbourne) and Gary Ablett (Gold Coast).

Cornes reached his 250th game in Round 5 of 2013, where Port Adelaide came from 41-points down to win 12.12 (84) to 10.19 (79) at AAMI Stadium against the West Coast Eagles, taking the Power to a 5–0 start to the season.

[2] He finished his Port Adelaide career having played a total of 300 games, winning 4 best and fairest, two All Australian guernseys and a premiership.

Cornes took up a full-time media career in 2016 after a short tenure with the South Australia Metropolitan Fire Service, where he had been trying to do both, with appearances on The Sunday Footy Show and 1116 SEN, as well as writing for The Advertiser[3][4] and providing expert commentary[5] for AFL Nation coverage.

He has been known for some provocative commentary on leading AFL figures such as Patrick Dangerfield[6] and Hawthorn Football Club[7][8] in a challenging manner.