Nelson was impressive in Wednesday's EFL Cup third-round victory over Leicester City.
Asked after the game if Nelson would leave on loan this summer, Arteta said: "We don't discuss the things that are happening behind closed doors. He played tonight and he played really well."
Torreira was not included in the squad against Leicester, with speculation he is set to join Atletico Madrid.
When quizzed if Torreira's absence was due to an imminent transfer, Arteta said: "I cannot discuss any internal matters. I'm not making decisions because players might leave or stay.
"It's just for the players that we see every day in the best possible condition to compete and win football matches."