The 21-year-old midfielder has been a revelation for Posh since signing from Highland League side Cove City in July 2008 and Ferguson believes he has what it takes to make the grade for his country.
He said: "Paul is a great player and I have no doubts he will reach the very top at club and international level. He will play in the top flight and win full Scotland caps.
"He's an outstanding talent and the fact he is now playing well for his country does not surprise me in the slightest.
"I have to constantly remind myself how young Paul still is because he is so good I expect him to run the game for us even at Championship level.
"If he could just add a few goals to his game he would have it all."