Carroll joined Liverpool in a record £35million deal from Newcastle on January transfer deadline day.
“It was very disappointing how he was sold and we didn’t have the opportunity to replace him,” he told the Daily Mail.
“But hopefully the money will be wisely spent and it will prove a good bit of business for us – £35million is an incredible amount of money and time will tell.”
“He probably benefited from our relegation, got his chance and was a key part of us getting promoted,” Harper added.
“He had an unbelievable 2010. I’ve known him since he was 6ft 3in. We knew there was a player waiting to develop who could become a real handful.
“Great lad, keen, works hard on the training ground, and he was settling down under Kevin Nolan.
“He has a fantastic opportunity at Liverpool and a manager who will nurture and help him, as Dalglish did with a young Alan Shearer.”
