Stelios put in a man of the match display in Saturday's win over Middlesbrough in only his second full start for the club and the Bolton manager Allardyce has backed the 29-year old to improve on that display.
"Not too many people realise this lad is one of the top three players in Greece," the Wanderers' boss said.
"He's won seven championships on the trot and, because Greek football isn't publicised that much in this country, we've managed to pinch him.
"As time goes on he'll not only show his qualities on the ball, he'll also show his bravery. He was brave both from an attacking point of view and from a physical point of view. Even though he's only a small lad he can handle the strength and the pace of the Premiership."