The knocks I've heard against De Castro are twofold. One is that despite his intellect, his judgment sometimes strikes people as off. A good example is perhaps when he rose at the All Things D conference a couple of years ago to ask Apple's ( AAPL) Tim Cook why he was in the ad business. Why do you try to embarrass the CEO of your biggest competitor in front of all your tech peers? What's the upside to you of doing that? The second knock, relayed to me from a former co-worker of De Castro's, is: "When I heard Henrique was going to become Yahoo!'s COO, I thought, I can see him being 'chief' and I can see him being 'officer' but what I can't see him doing is 'operating.' That's just not Henrique." I'm long Yahoo! and a big reason why is I believe that the core can return to greatness. Turning the ship on sales will be a big part of that, and that falls under De Castro's purview. I want him to succeed. But, 10 months into the job, I think he needs to take responsibility for the state that sales is in now and a good look in the mirror. He has a number of strengths. I truly hope he also sees his weaknesses as well and is prepared to embrace them and ensure he's got people around him to help cover them off. If the sales don't turn around -- and if Tumblr doesn't deliver a meaningful bump in sales and Ebitda next year -- it will be De Castro's head on the line - not David Karp's or Marissa Mayer's. As of now, De Castro is officially on the hot seat at Yahoo!. At the time of publication the author was long YHOO and AOL.Follow @ericjacksonThis article was written by an independent contributor, separate from TheStreet's regular news coverage.