Iñaki, who was named Man of the Match for his impressive performance, said the win proved to the world that Athletic are a match for any side.
“I’m very happy,” Williams said after the final. “But I still haven’t processed what we just did.
“We showed we can compete with any other team. They couldn’t knock us down.
“Personally, I’m very happy. When I needed to turn up, I was there and the ball went in.
“It’s the reward for all the work I’ve been doing.”
The striker said it was hard work and a refusal to give up that saw Athletic over the line.
“The effort made and fatigue didn’t get the better of us,” he added. “We never accept defeat. That’s our style. And when we fight and battle together, we’re very difficult to beat.
“We showed that we’re a great team and this is dedicated to all Athletic fans.
“When you have heart and faith, all is possible. We’ve worked like animals and we’ve been rewarded for it.
“I think we’re deserved winners of this Super Cup.”
Global TV Guide: Levante UD vs Athletic Club (LaLiga Matchday 25)
When and where to watch Athletic’s upcoming LaLiga match against Levante UD
Marcelino: “We’re focused on winning tomorrow”
Marcelino looks ahead to Friday night’s LaLiga Santander match against Levante UD
Squad list: Levante UD vs Athletic Club (LaLiga Matchday 25)
Marcelino has called up 23 players for Friday night’s clash with Levante UD at the Ciutat de València
A big week against Levante
Athletic will face Levante twice in six days, starting with a LaLiga fixture on Friday (21:00 CET)
Raúl García: “The more difficult the challenge, the better”
After extending his contract with Athletic Club until 2022, Raúl García expressed his intention to keep going “as long as he was up to the task of competing for this Club”
Raúl García signs contract extension until 2022
The agreement includes an option for a further season depending on a number of targets.
Berenguer in top goalscoring form
Athletic Club’s most recent signing is our current top goalscorer with six goals, four coming in his last five appearances
Highlights I Athletic Club 1-1 Villarreal CF (LaLiga Matchday 24)
Athletic pick up a point in a tightly-contested match against the Yellow Submarine at The Cathredal
Marcelino: “Athletic deserved to win”
Marcelino praises the attitude of his Lions, despite the draw against Villarreal
Berengeur on target in draw with Villarreal
Athletic’s current top goalscorer equalised after Gerard Moreno put Villarreal in the lead