"I normally call him the beast," Frank told Sky Sports. "He's a remarkable player and person. He's so dedicated. Of course, he wants to be top scorer, but that's not his main aim.
"He's so dedicated to improve every single day, so he's a coach's dream because of course we want to focus on little details. We've been working very hard on his positions and how to run in the box and the link up play."
Frank added: "Overall he's just improved massively as a player and also as part of the leading group," Frank added. "He's driving the team. Look out there how hard he works – it's a joy to have a striker like that.
"He's one of the hardest, if not the hardest working offensive player in the league, and he's also the top scorer. That's not a bad combination."