Both sides had a number of opportunities in an open first period, but neither could make the breakthrough after 45 minutes of football.
Chances were at a premium in the second half, however, as the two teams played out a goalless draw in the first leg.
Read how it all unfolded in Sports Mole's minute-by-minute live commentary of the action below.
GIMNASTIC: Tomeu; Juanjo, Campos, Mari, Verdu; Sanchez, Rocha, Luc, Lago; Giner, Marcos
VALENCIA: Alves; Barragan, Costa, Mathieu, Guardado; Parejo, Oriol; Feghouli, Canales, Bernat; Jonas