Finnick knows how to be quiet when he tries. But he's not particularly trying, because he knows better than to sneak up on a man practicing with a blade. He doesn't realize until the man turns that he's blind, blind or injured to judge by the bandage on his eyes. That makes what Finnick had seen of the swordsmanship even more impressive, and it had been impressive enough. Finnick's never been a swordsman by choice, though as a Career he'd of course had a couple of years of training. But there'd always been things he was better at: spears, knives, tridents. And he'd known he'd probably never actually have to rely on using a sword for long.

So Finnick replies lightly when the man turns to him.

"I think you're out of my class."

It's something of false modesty; though he doesn't have a sword or skill as a swordsman, he does have his trident, and he's famous for his skills with that.