Healy enjoyed a productive spell at Deepdale and then spent three years at Leeds before Lawrie Sanchez offered him a Premier League chance this summer.
But it is with Northern Ireland that Healy has made the biggest impression, scoring a record 13 goals during the Euro 2008 qualifying tournament.
"David has been fantastic," said Ferguson. "When he was here as a young lad, David was blocked from making progress simply because at the time, we had four top strikers.
"We got a very good offer from Preston, which let the boy get on with his career and his form for Northern Ireland has been amazing.
"To score 13 goals from a country which is nowhere near one of the top sides in Europe is absolutely brilliant."