Is it because Darrow was injured?

When karnus and his cousins attacked Darrow just after academy defeat at a pool, why Darrow couldn't fight them? He is already trained by Lorn by then., is it just because his hand is injured and theyy were 7 or he didn't purposely show his training by Lorn. PS- i know he cannot take all of them at once,but also he knows that they won't kill him.