Sunderland manager Dick Advocaat was worried supporters would walk out on his side during their 4-1 League Cup home defeat by Manchester City.
City were 4-0 up inside 36 minutes at the Stadium of Light, but most Black Cats fans stayed until the end.
Advocaat told BBC Radio 5 live: "I was a little bit scared to be honest and thought hopefully the fans will stay - and they did.
"I said we cannot go on this way because City will get double figures."
Advocaat was pleased with his side's start against a City team that had lost their previous two games - to West Ham in the Premier League and Juventus in the Champions League.
But once Sergio Aguero had given the visitors the lead, Sunderland conceded three more goals in 27 minutes to leave the Dutchman fearing fans would leave en masse.
In March, a large number of supporters walked out when the Black Cats were 4-0 down to Aston Villa in what turned out to be Gus Poyet's final game in charge.
"We gave three goals away and even then they could have made it four, five or six nil," Advocaat said.
"At half-time I told the players, 'now you have to fight for each other and work for each other. Otherwise we make a fool of ourselves.'"
City named a full-strength team including record signing Kevin de Bruyne, Raheem Sterling and Aguero. All three scored, while Vito Mannone added an unwitting own goal.
"We had a team meeting in the afternoon and we heard that they had a lot of other players in the team," Advocaat said.
"And then we get the line-up and they named their strongest side. It is difficult to play a team like City when they play like that.
"In the last 15 minutes of the first half we didn't get the ball back."