The Rams were in contention of a top-six finish for most of the season, but on Saturday their hopes of playing in the 2015-16 Premier League campaign were dashed.
Steve McClaren’s side could have made it to the playoffs had they picked up just a point against Reading at home this afternoon, but they lost the encounter 3-0.
Derby had been in the top six of the Championship since September, but just two wins from their final 13 games will go down as one of the biggest disappointments in their recent history.
Warnock, who joined the Rams from Leeds United in the January transfer window, has now expressed his disappointment on Twitter.
The 33-year-old former Liverpool left-back has also thanked the Leeds and the Derby fans for their support.
Another season over. Big thanks for the support from both sets of fans I played in front of this season. A disappointing way to end though.— Stephen Warnock (@StephenWarnock3) May 3, 2015