Alan Shearer finds it "staggering" that Newcastle allowed striker Andy Carroll to leave for Liverpool without bringing in anyone as a replacement on transfer deadline day.
Carroll, 22, joined Liverpool late on Monday for £35million, a British transfer record that was quickly broken when the Merseysiders sold Fernando Torres to Chelsea for a fee believed to be around £50million.
"I'm staggered just like the rest of Newcastle fans," Shearer told BBC Five Live: "I am surprised at how quickly it came along and it's an astonishing amount for a young guy with huge potential."
He added: "It's all right selling your best player, but not getting anyone in to replace him is staggering.
"People are saying that Liverpool have sold Torres, but they have got two guys in for over £50million to replace him. I just hope Newcastle invest some of the Â£35million in new players at the end of the season.
"I am disappointed as he is Newcastle's best player and their best hope of being successful this season and getting a Europa League place. They would have just been happy to avoid relegation at the start of the season but, mainly because of him, they had a chance of a Europa spot."
But Shearer believes that Carroll will only get better while working with Liverpool manager Kenny Dalglish.
"He is a huge loss, he has carried Newcastle at times this season. There are not many players like him," said Shearer. "He is big, strong, very good in the air and has a good left foot. You get that ball in the box and there aren't many that could stop him, but he will be a tremendous asset to Liverpool.
"Having worked with Kenny Dalglish I can tell you he is not only a great man, but a great manager. If anyone can get the best out of him then Kenny will.
"To work with one of the greatest football figures of the last two decades, I know he will learn the tricks of the trade from him and improve."