The 23-year-old defender, who joined Liverpool from Nacional in 2011, linked up with the Black Cats on a season-long loan during the summer.
Asked if he has hopes of remaining at the Stadium of Light beyond this season, Coates is quoted by the Sunderland Echo as saying: "I don't know. I'm focused on playing some games this year and improve in the Premier League. I want to show why I am here.
"Maybe I expected it to be a learning experience [at Liverpool]. It's hard because it's a great club and there was a big squad, with a few defenders.
"For me, it was good because you learn every day. But the manager can only choose two guys to play. I decided to come here to get the chance to play so, for me, it will be great to play some games."
Coates spent the second half of the last campaign on loan at former club Nacional.