Newcastle United goalkeeper Steve Harper fears how the club would handle relegation.
Harper told the Sunday Sun: "When I was first involved at this club, we were also in what is now the Championship. It would be awful if we went down.
"I've played in that league so I know how tough it is and how tough it would be to get out of it when people would expect us to bounce straight back if the worst was to happen. But we try not to think about that. If we need to think about that on May 25, then we'll all be devastated.
"We have three games to avoid that, starting on Monday night. It's the biggest game I've been involved in in my time here. We keep saying that it's the biggest game - but this one really is.
"Derby-wise, the Sunderland game was massive. They had the better of the first half and we had the better of the second, but we have to put a 90-minute performance in on Monday. It's a must-win."