Bruce says the Newcastle play-maker has added intensity and running power to his “natural gifts," and helped the Geordies to a six game unbeaten streak in the league.
He reckons Shelvey has bought into the role of bossing his team's possession play.
Bruce, whose side face Manchester City on Wednesday, said: “Jonjo understands what we are trying to do. As a footballer all the things that come naturally to him are the most difficult.
“What he has done is add to his natural ability. He has added a physicality to it, getting up and down the pitch. At the moment he is the complete midfield player.
“With the top players, that is what they can do. Jonjo more than anyone has gone to town on what he can do physically and we are reaping the benefits."