West Ham captain Mark Noble has written an open letter to fans pleading for unity after disturbances at their last home match against Burnley.
Noble confronted a supporter who went on to the pitch during the 3-0 loss at London Stadium on 10 March.
Saturday's Premier League home match against Southampton is the first since that defeat, after which 20 fans were given life bans by the club.
"We need everyone to be together," said Noble, 30.
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In the letter published on the club's website, Noble said the match against Burnley was "one of my toughest days in nearly 20 years at West Ham, and I never want to see scenes like that again".
Angry fans invaded the pitch and congregated below the directors' box to protest against the club's owners David Gold and David Sullivan, with the latter reportedly being struck by a coin.
The club have announced a security barrier is to be installed at the ground to prevent supporters getting too close to the directors' box.
West Ham are 17th in the Premier League, one place and two points above Southampton and the relegation zone, with eight games remaining.
A further protest has been planned outside the ground before Saturday's match, but Noble has urged the fans to get behind the team during the game or face the prospect of dropping into the Championship.
"We need you all, full-stop, and we cannot perform to our best and win the matches we need to win without you. When you are on song, there really are no supporters better at inspiring their team than West Ham supporters," he said.
"I can understand the frustrations some of you are feeling. This season has not gone how we'd all hoped it would, but I would ask you to channel your passion to get behind the team, help us get through the season with our Premier League status intact, and we can sit down and reassess things in the summer.
"We need the London Stadium to be buzzing for our five remaining home games, so please unite behind the lads and give us the best possible chance to deliver the results we need to stay up."
Last week, London mayor Sadiq Khan said the stadium operators - not West Ham - would be responsible for meeting the extra cost incurred by the demand for greater security, policing and stewarding in the wake of the trouble at the Burnley game.
A Football Association investigation is continuing but West Ham have been warned by the body responsible for allowing fixtures to proceed that any repeat will result in them being forced to play matches behind closed doors.