Downing is expected to complete his £18m move to Anfield from Aston Villa later today and his addition to the squad has really pleased Carra.
"It's a terrific signing, there's no doubt about that whatsoever," said the Reds' vice-captain.
"He's been a top player in the Premier League for the last six or seven years and he will definitely make a difference, with his ability to go outside and down the line to get quality crosses in.
"I know him, so does Stevie; he knows Andy Carroll and Johnno (Glen Johnson) from playing for England, so he is not going to be walking into a dressing room and be on his own. He will get a great welcome because he's a good lad and a top player as well.
"He was Aston Villa's player of the year and he will give us something that we have been lacking, genuine quality on the left hand side. Every team looking to compete needs quality players in each position and that is what we are getting back towards."