The left-back has been impacted by an ankle problem for most of the season.
However, he believes that by putting in the hard yards, he can recover the form he showed last term.
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Estupinan told TV reporters while on international duty with Ecuador: "I'm struggling, I've had problems with my ankle.
I'll try to go back and see what to do to be 100%.
I have wanted to be with the national team, to fight for it, but there are no excuses.
"I try to give my all and I will continue working."