Sevilla shrugged off an early shock from Primera Division new boys Levante to run out comfortable 4-1 winners.
Ruben Suarez put the hosts ahead with a 10th-minute penalty, but Abdoulay Konko levelled two minutes later and Alvaro Negredo put Sevilla ahead from a dubious spot-kick.
Right-back Konko grabbed his second after 62 minutes before Renato rounded off the scoring two minutes from time.
Fernando Llorente's goal just after half-time was enough to give Athletic Bilbao an opening-day 1-0 victory in the Primera Division and spoil Hercules' return to the top flight.
Llorente, a World Cup winner with Spain earlier this summer, headed home from a free-kick to seal the points for Athletic in Alicante against a Hercules side who finished the match with 10 men following the dismissal of Matias Fritzler in the last minute.
Hercules started the match without any of their three summer signings, including Paraguay forward Nelson Haedo Valdez, while experienced midfielder Javier Farinos was also missing through injury.
Joaquin Sanchez netted a second-half brace as Valencia began life without star duo David Villa and David Silva with a 3-1 victory over Malaga.
Villa and Silva were both big-money departures from the cash-strapped club this summer, along with fellow World Cup winner Carlos Marchena, but Unai Emery's side still enjoyed a winning start to the new Primera Division season after seeing off Malaga.
Aritz Aduriz, signed from Real Mallorca this summer to help fill the gap left by Villa, enjoyed a dream league debut for Los Che as he opened the scoring after just 10 minutes.