I think Williams will be behind Ferrari and Force India/Toro Rosso will start the season close to Red Bull.
Based on a more detailed analysis I read, this appears to be the case, with Williams being in the mix with Red Bull, Toro Rosso and Force India. Renault are only a little further back, with McLaren and Sauber doing their own thing further back still. Ferrari also looked closer to Mercedes than they were last season, with the pair being a long way ahead of the midfield squabble. Ref:
2016 Preseason Form Guide