Is this some kind of joke? What makes you think Diaby has "steel" and strength? Is it because he's tall and african? The guy is a skilled and relatively creative midfielder with an immense ability to drive forward with the ball. He's most certainly not a physical a holding midfielder.
Second of all, Diaby can barely even play a minute of football without getting injured. If you want a physical footballer then Diaby is the last one on the list...
The guy might eve have to retire because of all the injuries. He's been robbed of a brilliant career.