The Spaniards, who will take on Moyes's side at Old Trafford tomorrow night, have so far failed to replicate the form that they showed last term and sit 12th in the La Liga table.
However, Moyes has insisted that there is still plenty to be wary of, despite the fact that key players such as Asier Illarramendi have departed the Basque outfit.
"I watched Sociedad a lot last year and was really impressed by how well they did," the Scot told reporters. "The loss of one or two players has made it harder for them this year and maybe the expectations have been much bigger. The games I've watched I've been impressed.
"They change their style with one defensive midfielder and sometimes two. They had a good result at Valencia on Saturday and we have to be mindful of what they can do.
"Old Trafford is a big place to come and play football but it's also an enjoyable place. We hope they don't enjoy it too much."
Sociedad go into the clash having lost their opening two group fixtures, while hosts United have amassed four points.