McMullan has had nightmares about Forrest since the Celtic winger gave him a hard time in the first leg of their Champions League second qualifier in Belfast last week.
The Scotland wide-man was in top form against the Northern Irish part-timers and scored the third goal in a convincing 3-0 win for the Scottish champions which means Tuesday night's return leg in Glasgow should be a formality.
Speaking at Celtic Park before Cliftonville's training session tonight, McMullan said: "I am not the quickest so I have been having a few nightmares about him running past me.
"We were hoping that playing against a part-time team that they wouldn't be on their game but they were.
"You watch Celtic year-in, year-out on television and they don't look as quick as they are but once they get the ball down and get a turn of pace it is frightening.
"And to be fair, their quality on the ball showed that it there is a gulf between our league and Celtic.
"So I have nothing but admiration and respect for Celtic and the way they played.
"And as much a nightmare as it was, it is actually good nightmares, ones I enjoy having."
Reds manager Tommy Breslin admits the game against Celtic is a damage-limitation exercise for his side who have been in Glasgow since Sunday.
He said: "In reality it probably is (damage limitation). We are not going out to roll over.
"I don't want to be on the wrong end of a drubbing and that could be a possibility.
"We are here to try to frustrate Celtic and try to give a good account of ourselves.
"But as an occasion we are looking forward to it. We know it is going to be a tough game.
"Let's put it into perspective, we are a part-time club. I feel we have the best players for our league but we are coming up against a team who were in the last-16 of the Champions League not so long ago. That's what we are up against."