The Magpies finished fifth in the league last season, but have faltered this year - and the Old Trafford boss says that the Magpies are now being analysed thoroughly by opponents
Alan Pardew’s side finished fifth in the table and saw the former West Ham man take home the LMA and Premier League Manager of the Year awards, but now the Magpies are in a lowly 14th position in the table.
"The new players they brought in caught us all by surprise," Sir Alex told reporters.
“We didn't really know a lot about them. I knew about [Demba] Ba, of course, but I didn't know anything about [Yohan] Cabaye or [Papiss] Cisse, to be honest with you.
"They had fantastic seasons. Second time round, clubs are starting to analyse them a bit different, plus, more importantly, he's [Pardew] had some injuries.
"Cabaye's out till next year, [Cheikh] Tiote is out to next year, he's had one or two important players injured and that does make a difference when you've not got a squad as strong as the likes of ourselves or [Manchester] City or Chelsea.
"I'm not entirely surprised [by their form], although I am surprised they are so low down the table."