Nottingham Panthers netminder Dan Green says beating Sheffield on Saturday is vital to their title hopes.
Panthers are currently four points behind Belfast and level on points with Steelers, who have four games in hand.
Green told BBC Radio Nottingham: "I don't think we played badly the last few games but we struggled to beat Fife and lost to Belfast and Cardiff.
"We really have to win Saturday and Sunday [in Fife] and then we have to win in Sheffield next weekend. "
Panthers have beaten Steelers twice this season with two victories in Challenge Cup Group B.
But since securing their semi-final spot with a 3-0 victory over the Steelers at the National Ice Centre, Panthers have lost three of their last five matches.
"We haven't been as good the last few weeks," added the former Steelers netminder. "The two games against Sheffield were two of the best games we played this year.
"The rivalry is definitely massive. Since I have been there's a rivalry with Coventry and Belfast, but Sheffield is the biggest.
"If you lose a Sheffield game you really feel it for a week or so."