Harewood played alongside Carroll during a loan spell at Newcastle in 2009 and hopes the former England striker can rediscover his best form and silence his doubters.
"Andy can give any defender problems, and I loved playing with him and feeding off him," Harewood told Sky Sports News.
"We formed a really good partnership. He's since had rotten luck with injuries but Andy is still a top-class player.
"He is one of the best headers of a ball in the Premier League but the key is getting him fit and back on the pitch.
"The setbacks must be really hard for him but that's football. I hope he bounces back and has a really good year to silence some of his critics."