Arsenal defender Gabriel has been ruled out for two to three weeks after suffering a hamstring injury in Wednesday's 2-1 win at QPR.
he 24-year-old Brazilian defender was forced off in the 36th minute of the game at Loftus Road. It was only his third start for the Gunners.
Gabriel, who was signed from Villarreal for a reported £11m in January, will miss Arsenal's FA Cup sixth-round tie at Manchester United on Monday, a game that Wenger says has a "special intensity".
"It's a special intensity because it's between two teams with a chance of winning," the Frenchman said. "We're focused on the FA Cup.
"We are the holders of the FA Cup and we want to keep it. The cup is about giving it all on the day and we'll do that on Monday.
"We are confident. We go to Manchester United to qualify and give absolutely everything with hard work and team effort."