Warnock made his first-team debut for Liverpool against Grazer AK on 10 August 2004, in the first leg of a UEFA Champions League third qualifying round match.

[7] In a media speculated swap deal, Blackburn's captain Lucas Neill was reported to being changing clubs with Warnock in both summer 2006 and winter 2007.

[16] From December 2010 onwards, Warnock was out of favour with Aston Villa manager Gérard Houllier and was forced to play with the reserve team.

[17] Warnock was widely expected to leave the club in the summer transfer window, with a number of teams reportedly interested in his signature.

[citation needed] During the 2012–13 season under new manager Paul Lambert, Warnock found his chances limited and was made to train with the development squad.

[22] He was on the bench a day later in their 2–1 win against Sheffield Wednesday and made his debut in their next match, starting at left back in Bolton's 1–0 defeat against Crystal Palace.

[25] He made his Leeds debut on 9 February 2013, playing the whole match in the club's 2–2 draw against Wolverhampton Wanderers at Molineux.

[42][43] After impressing with Aston Villa in the early 2009–10 season Warnock received a call up to the international squad once more for a friendly against Egypt.

[45] On 1 June 2010, he was named in the final 23-man selection by manager Fabio Capello, ahead of other left back Leighton Baines.

[46] Due to the widely accepted adeptness of Ashley Cole at left back, Warnock did not feature in any of England's matches during their short-lived run in the World Cup which ended against Germany.

[55] In 2024, Warnock took part in the Sky Sports News Real Talk series, where he opened up about his struggle with depression and suicidal thoughts following his retirement from football.

[56] Recently, Warnock has been involved as a brand ambassador for Golfclubs4cash, Europe's largest retailer of second hand golf equipment and accessories.