The Norway midfielder recently penned a new four-year contract with Rovers.
Allardyce told the club's website: "Yes he had some golden years at this football club, where he was an outstanding individual, who scored many goals and provided many goals, but once we moved him into midfield it took the pressure off this perception that he was never as good as he used to be.
"His contribution is still a huge one. Perhaps not as big as it used to be, but moving him inside and off the wide position has been a great move for him and a great move for us, because he's got less pressure on him to provide the sort of goals and the sort of crosses that he did before.
"Now he's coming from the middle of the field, he's making more accurate passes and getting more involved in the game in possession terms.
"He's an outstanding deliverer of free-kicks and 60 per cent of our goals were scored from set-plays last year, which was one of the best in the Premier League. He's got a long throw as well.
"So when you put his armoury together as a whole, he's a very productive player for us in terms of trying to create and score goals. And since we moved him into midfield, we've seen much better and much more consistent performances from Morten."