Victory over United, who have been revitalised under Ole Gunnar Solskjaer, in the huge Molineux encounter would set up a trip to Wembley in the last four.
The excitement among fans for the 7.55pm clash is palpable, but Saiss and Co are not getting caught up in what might be. Focus is firmly on United and stopping them from playing.
"We have to switch on for this game now," said Saiss.
"It’s an important game for us to get the semi-final at Wembley.
"We play at home, and we have to be ready for this game.
"We’re going to prepare for this game all week now and try to do something great on Saturday.”
Wolves are heading into the tie on the back of a 1-1 draw at Chelsea, which took their points tally against the Premier League's top six this campaign to 10.
One of those points was at Old Trafford back in September too.
United, meanwhile, suffered a somewhat surprising 2-0 defeat at Arsenal on Sunday.
On the performance at Stamford Bridge, which saw Raul Jimenez's strike cancelled out by a last-gasp Eden Hazard leveller, Saiss said: "It was very hard to concede this goal at the end because I think our plan was good.
"We respect the plan and tried to frustrate them, and tried to do something when they made some mistakes.
"We did it well but, unfortunately, we didn’t keep the result until the end so it’s hard, but we can be proud because we did a lot of effort. We have to keep moving forward and continue in this way.
"We can be proud because to play against a very good team, who play some of the best football in this league, is hard.
"I think we could have achieved something great today and kept the win, but it’s football and we have to learn.”
And the vital thing Saiss and Wolves learned against the Blues is not to lose concentration for a split second.
“The plan was to stay compact, close to each other, and wait for the mistake of Chelsea, then when we’ve got the ball, try to keep it and do something," he added.
"We did it a couple of times and got one goal, but unfortunately we conceded.
"We knew it was one of the best teams in the league.
"They have a good tactic and good play, so we knew we had to stay focused every minute, every second.
"We know a player like Hazard can change the game at every time so we have to be ready for that and, in one shot, he scored.
"I think we deserved more because we gave everything on the pitch, so it’s a little bit hard but that’s football.”