The Newcastle United defender, signed from Atletico Madrid last summer, made only his second Championship start for the league leaders in last night's goalless draw at the Madejski Stadium.
With DeAndre Yedlin sidelined with a thigh problem and Vurnon Anita being eased back following his spell out with an ankle injury, Gamez was named in Benitez's starting XI.
"We have a problem with Yedlin, because he had a knock against Brighton," said Benitez. "It was worse than we were expecting. Anita was playing after six weeks."
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Gamez's previous league start came in November, when he was stretchered off against Blackburn Rovers with a broken collarbone.
While Benitez acknowledged that he was not an easy game for the 31-year-old to come into, he felt the former Spain Under-23 international acquitted himself well against Jaap Stam's fifth-placed side on a difficult pitch.Jesus, I think he was fine on the ball. He's fine and he has experience.
"He knows his job," Benitez told BBC Radio Newcastle. "Defensively, it was not an easy game, because they have some pace. But I think he was OK.
"When you have a new player playing, you cannot expect that he will be the best in the team, but I think he did fine."
Meanwhile, the club's medical staff after continuing to assess Yedlin, who suffered the injury in last week's win over Brighton and Hove Albion at the Amex Stadium.
Yedlin, signed from Tottenham Hotspur last summer, came off the bench against Huddersfield Town at the weekend.
Meanwhile, Anita is likely to start at right-back against Fulham at st James's Park on Saturday.
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