The former Spain forward and Champions League all-time top goalscorer has been at the heart of Schalke's run to the last four. After leaving Real Madrid last year after 16 trophy-rich seasons, Raul has scored five times for Schalke in the competition while the Bundesliga side have won five out of five at home.
United know all too well of Raul's qualities as a matchwinner, his two goals for Real at Old Trafford in 2000 knocked the current Premier League side out of the competition.
Schalke's demolition job on holders Inter Milan in the last eight will also have left United in no doubt that the German outfit are no soft option, a view that should be reinforced by their poor record against Bundesliga sides.
Although their most famous victory came over Bayern Munich in the 1999 final, United have lost all four of the two legged knockout ties they have played against German sides since the start of the Champions League in 1992.
"The German teams have always had a resilience and determination about them and that will be exactly the same on Tuesday," said Sir Alex Ferguson, whose side lost to Bayern in last year's quarter-finals.
"But we're going into this game with far more experience than in previous years and our experience away from home, and our record, in the last few years has been terrific."
Schalke coach Ralf Rangnick rested several players in their 1-0 home defeat to Kaiserslautern on Saturday.
"We will have a different starting team against United," said Rangnick, who took over from sacked Felix Magath a month ago. "If I had chosen the same team on Tuesday that I did today I don't think we would have a big chance to win against Manchester."
Peruvian Jefferson Farfan, who missed the quarter-final second leg against Inter, will be back in midfield while defenders Benedikt Howedes, Atsuto Uchida and Hans Sarpei should also return.
SEMI-FINAL DEBUT
Midfielder Jose Jurado, who came on as a substitute on Saturday, is also expected to start in Schalke's maiden Champions League semi-final appearance.
Schalke, despite being 10th in the Bundesliga, still have two titles to fight for this season with the Champions League and their German Cup final against second division Duisburg in May.
For Schalke's 25-year-old captain and goalkeeper Manuel Neuer, who is set to leave in the summer after a staggering 20 years at the Ruhr valley club, there could not be a more appropriate farewell.
"Manchester may have won their last league game but it was not all victories before that. So we know very well that we have a chance against them on Tuesday."
United beat Everton 1-0 on Saturday to close in on the Premier League title.
Defender Nemanja Vidic and midfielder Michael Carrick are set to return after being rested.
Although he knows the value of an away goal at this stage, Ferguson would probably be delighted to come back with a 0-0 draw given the incredible form his side have shown at Old Trafford this season.
