United won the first group match between the clubs 1-0 at Old Trafford with an own-goal.
And Carrick said: "It was tight. People have been writing off Sociedad because they haven't had great results this season but they are still a good team.
"Going over there will be tough but we know if we are close to our best, we'll have a good chance.
"The Champions League group stage is about picking up points and the home games are the big ones. They are vital and we have managed to win both so far in this group.
"If we can go away and get a good result we will be in a good position and the situation looks good in the group at the moment.
"But it could soon change after the next set of games and we have to guard against that."
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