Sunderland chairman Ellis Short admitted mistakes had been made during his tenure after the club slipped out of the Premier League on Saturday.
A 1-0 defeat to Bournemouth, courtesy of Joshua King's late goal, condemned David Moyes' side to the drop after 10 years in the top flight.
Short and Moyes have come under fire from supporters in recent weeks and the American conceded player recruitment had contributed to their demise.
He said in a statement: "I am truly sorry that we have not been able to retain our top-flight status.
"I acknowledge that during my ownership mistakes have been made, particularly in the area of player recruitment, and as a result we have found ourselves struggling to survive in recent seasons.
"We had massive disruption during the summer transfer window and an unprecedented number of injuries throughout the season. These are difficulties which we have been unable to overcome and we are paying the price for that now.
"We need to improve, both on and off the field, and despite the bitter disappointment of today there is a strong determination to do so throughout the club.
"There is significant work to be done over the summer and when the season is concluded, we intend to share our plans to move forward with our supporters."
Sunderland have four games remaining this season, taking on fellow strugglers Hull City and Swansea City before facing Arsenal and league-leaders Chelsea.