The Stags need only a point to guarantee a spot in the play-offs next weekend, but saw their automatic hopes all but extinguished after a 2-2 draw at promotion rivals Salford City in today's televised lunchtime kick-off.
“We now need a point against Forest Green to guarantee play-offs so we must not lose the game. It's perfect clarity,” said Clough.
“It would have been nice to have a chance of automatic, but with Bristol Rovers' home fixture with Scunthorpe that is highly unlikely now.
“But anything happens on the final day – you never know. Funny things happen and we just have to make sure we do our job.
“Forest Green will need to win it to have a chance of winning the league. They have been up a week or two now. But I am not interested in them. It's about what we do.
“The players are disappointed in there as they know, realistically, we haven't got a chance of automatic now. That's gone and they have three or four days to get over it, clear their heads and get ready for Saturday.
“We are still in with a chance going into the last day. That's the main thing and our fans have backed us all season.
“They have seen a team have a go today and create enough chances to win a game.
“From where we've come from, second bottom a few months ago, to be in with a shout on the last day is brilliant.”
He added: “Individually, when you get such a big game and TV cameras are here and everything, I think four or five players did not perform to their abilities.
“They will be disappointed with that. But for some of them it was their first experience of a game of this stature, even at League Two level.
“We just needed to relax and play our stuff. When we did it was excellent. But we didn't do it enough today.”
Clough was disappointed to see his side give away two goals from free headers.
“Both teams had to go for it, but I am bitterly disappointed with the goals we conceded - two headers from the middle of our goal unchallenged,” he said.
“Ultimately that was what cost us the game and our lack of being clinical in the final third.
“We had enough situations throughout the game.
“After they scored, for 20 minutes we were absolutely brilliant.
“We were calm and composed, got the goal back, and then for some reason stopped doing what we had been doing in that period and they got back into it.
“We got a break with the penalty on half-time then conceded another poor goal in the second half.
“But we had chances and situations to win three or four-two, especially at the end.
“They had to win so they were going for it and leaving spaces, but unfortunately our front three or four didn't exploit it.
“We were looking for someone to produce a little bit of quality to win the game.
“Rhys Oates on another day would have had two or three goals today.
“They had situations at the other end, though Bish (keeper Nathan Bishop) has not had too much to do.”
Veteran talisman Stephen Quinn again missed out with his hip injury and Clough said: “He tried to train yesterday but it was pretty sore. It's just how it heals and how he feels in the next few days.
“We certainly missed his composure today. It was all a bit frantic.
“We have to try to avoid that as it doesn't suit our style.”