Kwiatkowski may be better known for his results in the Ardennes Classics, but he laid down a marker for the cobbled Classics after breaking clear with Sagan on Karnemelkbeekstraat.
Sagan instigated the move, but the two men worked well together to hold a short, but decisive lead all the way to the final straight.
And in a race Team Sky also won in 2015,
through Geraint Thomas, it was the Pole who prevailed – accelerating with almost 300m to ride to ensure Sagan’s sprinting prowess did not come to the fore.
Earlier, plenty of attacking and counter-attacking had made for an enthralling race, with a mechanical costing Fabian Cancellara (Trek-Segafredo) when he was in a small front group.
Spartacus fought back despite having to wait several minutes for his team car, but the action continued apace – Sagan and Kwiatkowski having actually been missing from that selection.
They had returned to the front on Oude Kwaremont, where Niki Terpstra (Etixx-QuickStep) set the pace before Sagan counter-attacked to form a three-man leading trio – Lars Boom the third man.
Ian Stannard was also on the podium to cap a fine day for Team Sky (pic: Sirotti)