The Manchester United boss explained that players develop considerably in their mid-20s, citing Wayne Rooney and former United midfielder Cristiano Ronaldo as examples. But with Messi still just 24 and already Barcelona's record goalscorer, Ferguson believes the Argentina star could get even better.
“Players develop and start to mature when they reach 25 or so," he told The Sunday Mirror.
"We’ve seen that with Cristiano Ronaldo, Wayne Rooney and others. But Messi has not even reached that age yet. It’s frightening what’s going to happen – he’s only 24!”
Meanwhile, Ferguson revealed that he is hopeful United's Scottish midfielder Darren Fletcher - who has been missing for most of this term suffering with ulcerative colitis - may be able to play a part next season.
“Darren is coaching with the reserves and he’s going to start a programme quite soon to get his fitness up," he said.
“The big push will be pre-season to try and get him back to the level he was at.”