The winger has made an excellent start to life at The Hawthorns since joining on an initial season-long loan, scoring twice, including in the victory over Manchester United at Old Trafford.
And defender McAuley believes the quality Amalfitano has shown so far, suggests Marseille must have an embarrassment of riches in his position to have allowed him to go.
"He is some player," McAuley told the club website.
"I don't know who plays on the right of midfield for Marseille, but he must be decent.
"Morgan's another great player that the club have found.
"He mixes it up and he does a great job for us without the ball as well, which some people might not see but we certainly do as players."