Sir Alex Ferguson fears the emotion of Manchester United's visit to Liverpool on Sunday could have a negative effect on his players.
The game will be the first for Liverpool at Anfield since the damning findings on the Hillsborough tragedy were announced by an independent panel last week.
Liverpool intend to mark the match with a number of significant gestures and Ferguson has already appealed for calm from United fans in what is certain to be a tense atmosphere.
And having gone through something very similar four years ago, on the 50th anniversary of the Munich air disaster, the Red Devils boss accepts it may have a hidden impact. "It's a possibility, I don't deny that," said Ferguson.
"Human nature can be that way. When we played Manchester City for the 50th anniversary of Munich the place was so flat in the dressing room before the game. I even felt it myself.
"We just couldn't perform and were glad to get it out the way. It was such an emotional day for us and it could be that way on Sunday."
Having twice appealed for United's supporters to behave themselves, Ferguson opted not to deliver another plea, believing it would be pointless under the circumstances.
Instead, he wants the match to be played in the correct spirit, which will surely involve a pre-game handshake between Luis Suarez and Patrice Evra should both play.
"I don't think we should get into that now," he said.
"We should let the players get on with it. There is enough pressure on them. Liverpool have done their bit. We've done our bit. We've given a lot of messages so let the game go on."