Southampton have failed to live up to their standards in this campaign, captain James Ward-Prowse said after a 2-0 home defeat by Fulham on Saturday sealed their relegation from the Premier League.
Southampton are bottom of the table on 24 points from 36 games and will be heading back to the second-tier Championship 11 years after they were promoted to the Premier League in 2012.
The south-coast club earned a reputation as a leading developer of talent in a spell during which they finished in the top eight for four straight seasons, but they have gone from the brink of European football to being involved in relegation battles in recent years.
Southampton have finished 15th or lower in four of the last five campaigns, with their steady decline culminating in a dismal run this season, in which they have earned only six league wins, while racking up a club-record 24 defeats.
They are also under their third manager of the season in Ruben Selles, following the sackings of Nathan Jones and Ralph Hasenhuettl.
"It's disappointing. It is a moment that has been coming. We knew we had put ourselves in a difficult position," Ward-Prowse said.
"I believe we should be performing at a better level than we have done and we have not done that on a consistent basis. The standards have slipped away and that is why we are where we are now." Ward-Prowse, who came through Southampton's academy, has made 341 Premier League appearances for the club, but could leave in the close season transfer window.
"Over the last 10 years we have had that kind of consistency and that has wavered. It will be testing for everybody but these are the times that make you as a player and as a club, we have done it before and we will do it again," the 28-year-old said.
The club's owners Sport Republic described the relegation as "hugely disappointing". "We have fought tirelessly as a club throughout the season, but the Premier League is the most competitive league in the world and our results were simply not good enough to stay there," they said in a statement.