It was expected that the Costa Rica international would leave Craven Cottage during the summer, but despite links with the likes of Ajax and Werder Bremen, Ruiz, who spent the second half of last season on loan with PSV Eindhoven, remained with the West Londoners.
"It's been a tough month because there were some transfer options, but at the end there was no agreement between the teams and Fulham," he told the club's official website. "It is a bit hard because I felt like my time there was up, and I was looking forward to a new challenge, but it didn't happen. I still have a contract with Fulham, so I have to fulfill it.
"I'm a person who likes challenges and never backs down. It is true that I didn't expect to stay one more year, but I will face a new challenge, which is helping the team in the Championship.
"I feel physically good, fully motivated after the World Cup. I was expecting something else, but it didn't happen. Only God knows why things happen. Now it's my turn to help the team as much as I can. They have had a tough start after five matches they haven't been able to win. Well, it's a hard tournament, I'll try to provide experience and enthusiasm."
Ruiz joined Fulham from FC Twente for an undisclosed fee in 2011.