Here's a funny little detail I've noticed.
On Sporza (why I am reading a Dutch page when I can't read it? I just am ! Don't question my weirdness…) they've simply written Viviani as the winner for Hamburg last year, however, this year they obviously needed to specify a bit more... (they didn't specify which Viviani for London either.)
Depends on how you draw the line with sprinters. I'd say Kristoff is better for harder and bigger classics. And Sagan, Matthews if they count.
Viviani is a better classics rider than literally all of the pure sprinters. Smooth on the cobbles and fine on longer (3-4%) climbs but he still need one of the big classics. Either Milano Sanremo and/or Gent-Wevelgem.