Vettel had a couple of laps on the new softs, as Mercedes felt the need to pit Rosberg first (though still missed out on getting Rosberg out ahead of Vettel).
I really didn't like that, they know very well that the undercut works well at this race but felt it better to possibly compromise Hamiltons race over Rosbergs.
Hamilton clearly knew nothing about it as he was asking after the pit stop what happened to the gap.