The Argentina international moved to United for a British record fee of around £60m back in August, and has settled quickly at Old Trafford.
Carragher was comparing Di Maria's arrival to that of Mesut Ozil's for Arsenal last season, and the Champions League winner thinks that it is the former who has impressed more than the German.
He told the Daily Mail: "Di Maria has scored three goals in five appearances since his £59.7m switch in August and will be the headline act at The Hawthorns on Monday night.
"He has looked every inch a superstar and no apologies have been needed with regard to his form.
"Ozil, by contrast, finds himself enduring more frustrations this weekend. A 'crack in his knee' may rule him out for up to 12 weeks but, even when he returns to full fitness, I find it hard to see the German leaving his unconvincing efforts of last season behind."
Carragher retired in 2013 after making 737 appearances for the Reds.