Martinez is delighted Scharner's eccentric ways have put a smile on the players' faces. But he insists he is not back just to raise spirits.
He said: "Everyone sees the outside, the dress sense and the haircut and they don't see the real professional underneath.
"What Paul really is, deep down, is someone that is in love with the game. His life is all about preparing himself to be in the best condition for match day.
"He hasn't played many games for Hamburg because he started the season with a niggly knee injury. But he is in pristine condition physically.
"He's fresh and ready for the challenge and he doesn't just know the club, he knows the league inside out.
"As a defender for us, he's as good as we can get and we're really excited about having Paul in this critical period of the season.
"He knows how to play in these circumstances and he's desperate to make a real difference in the backline."