The 70-year-old was unaware of the Spaniard's talents before his amazing start in the Premier League, which leaves him joint-top scorer with 12 goals alongside Robin van Persie
The €2.45 million summer signing from Rayo Vallecano has set the league alight with a blistering start to life in England, and is tied with the Red Devils' own Robin van Persie in the scoring charts with 12 strikes.
And the Old Trafford boss believes his side will have to be wary of the Spaniard ahead of their trip to the Liberty Stadium on Sunday afternoon.
"I had never even heard of [Michu] before he came to Swansea. In fact, I think I am going to have a word with our scouting department!" he told reporters.
"[Michael] Laudrup has tapped into the Spanish market a bit like Alan Pardew tapped into the French market for Newcastle, and in Michu he has got a very good player."
United lead Premier League champions Manchester City by three points, and a win over Swansea with their game in hand would send Sir Alex's side six points clear for Christmas.
However, the Swans' impressive 2-0 win away at Arsenal on December 1 impressed the 70-year-old, who says his team must be careful when dealing with Michu.
He added: "He is a good finisher. The two goals he scored against Arsenal recently showed that. He was really composed when he went through on the goalkeeper - there was no panic."
And while the Spaniard is an obvious threat for Michael Laudrup's side, the Scot feels this may play in United's favour, as they are now well aware of the attacker's talents.
He continued: "The fact that Michu has had such an impact so early at least gives us the chance to assess him.
"He can play up front, of course, but he can also drop into midfield so that they can bring in Danny Graham.
"Not knowing where Michu will play does give us a problem. We have to be aware of his threat."