User blog comment:AYET/A different talk about chapter 701/@comment-4899461-20130307205450/@comment-4899461-20130308065418

I never said he was "second strongest", just that he and Luffy are the two strongest members of this team. Given the talent contained in the current Shichibukai, I feel like it's a bit premature in the timeskip to say that any of the crew (besides Luffy, maybe) to say that they are on the same level as the current Shichibukai.

The only thing I can be sure of is that Law seems quite confident in his abilities (he thinks he can face down Doflamingo, thought he could do everything on Punk Hazard alone before the Straw Hats came along out of nowhere) and Law doesn't really seem like the overconfident type. So I think if he's confident it's because he really is strong.