Sirius/Theo.
Sirius noted the wavering of his attention, the brief closing of his eyes, and let his own eyes flick over to where Theo's had gone. It wasn't hard to find the source of it — he'd noted that Nott hung around a particular man quite a lot, and being deep blue and taller even than Sirius it wasn't difficult.
"Losing can occasionally be more informative than winning," he said idly, his eyes still tracking over what was going on between Theodore's man and the All American blond, though the lion's share of his attention was still with Theodore. "Winning is so easy that when I lose it usually means I'm playing with someone who is worth my time. I could tell you weren't a purist, but the confirmation is appreciated all the same. Do you want to get out of here, before they kiss? I don't mind sticking with you a while longer."