The Borussia Dortmund forward scored his first international goal as Norway were beaten 2-1 by Austria in their opening Nations League game and Lagerback feels that it will be the first of many for Haaland.
He said: "I've maybe been around too long but I have never seen a guy since maybe Messi or Ronaldo that developed at such a young age.
"That's very unique and he has all the possibilities to become a really world-class player - if you look at the offensive third of the pitch and in the box then he's already absolutely top class.
"He perhaps has a little bit more to do in the link play but being so young, he's already at a really high level. With the qualities he already has and his focused personality - if he can stay free from injury then he can be a really top-class player."
Norway will play Northern Ireland on Monday (07.09.20) evening in their second match in the Nations League and Lagerback was full of praise for opposition defender Jonny Evans, who is set to return for the hosts.
He remarked: "Of course there are some great players and some experienced guys, but now I have heard that Evans is probably back.
"He's a leader. I've had a lot of respect for him both with Manchester United and now Leicester.
"I think he's a very important player for them to get back in the team so if I would mention one player I would mention him."