Saturday's 3-2 defeat at the hands of West Brom left Hughes' team sitting bottom of the Premier League table having failed to win any of their opening seven matches.
Granero, who arrived in west London from Real Madrid during the summer transfer window, has placed the blame for the club's poor start to the season at the feet of the players, however.
"We're the ones who have to improve because the manager is great," Granero told reporters. "We all support the manager. We know he's the best manager we can possibly have.
"Most of the losses, for sure, are not his fault. It is our fault - the footballers' fault.
"Last week against West Ham he told us all what was going to happen and it happened - just as he said. We were warned so it was our fault, the people who were on the pitch."
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James Morrison gave West Brom the lead within five minutes at the Hawthorns and later goals from Zoltan Gera and Youssuf Mulumbu sealed victory for Steve Clarke's team despite strikes in reply from Adel Taarabt and Granero.
"In the last games, we have conceded goals at the beginning and after that it is very difficult to come back against English clubs," the 25-year-old reflected.
"We all have to be more focused and not concede early. I'm sure we can play much better if we're not losing from the start."
Granero, in addition, refused to count his first goal in English football as a positive, adding: "It means nothing to me. We didn't get the three points."