Seulgi was the first SM Rookie to be unveiled in December 2013, with a couple of short videos and a teaser photo. She was dubbed as the second Taeyeon back then, which was probably a bit too much even though she has a nice voice.
Seulgi singing Christmas Carol
Seulgi sweet cake visual video
SM Rookies is a pre-debut team to provide exposure for selected trainees from SM Entertainment. They were supposed to release some songs but Red Velvet is introduced first before anything solid from the rookies.