A series of injuries restricted him to only a handful of appearances in the 2010/11 season before a groin problem ruled him out for the whole of the last term.
However, he was back in the starting XI and straight back on the scoresheet in Thursday night's Europa League qualifying win which puts the Bundesliga club close to a place in the play-offs.
"I have not had a better day than this one for a long time," said the Dane.
"I am delighted that I am now pain free and that the coach believes in me."
Hannover coach Mirko Slomka said Andreasen had deserved his place in the team given how hard he has worked on his comeback.
"He is now back on the footballing stage," said Slomka on his club's official website. "I also told him before the game that he had to score a goal before he could come off the field."
For all the joys of Andreasen's goal, and the comprehensive victory, Slomka was not totally satisfied with his side's performance with three weeks to go before the start of the 50th Bundesliga season.
"There were a lot of technical deficiencies in the first half and these destroyed our rhythm," he said.
"Furthermore, I a few tactical mistakes crept in which made life difficult for us."
Hannover host St Patrick's at the Niedersachsenstadion next Thursday and they will be confident of being in the draw for the play-off round the following day.
