Spaniard Perez, who has scored twice for Arsenal since joining from Deportivo La Coruna in the summer transfer window, limped off in the second half of Tuesday's 2-0 League Cup victory after a tackle by Reading's Danzell Gravenberch.
Wales international Ramsey, whose only Premier League appearance this season came in the 4-3 defeat by Liverpool during which he suffered a hamstring injury, has been included in the squad for Saturday's trip to the Stadium of Light.
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Wenger felt that the tackle on Perez was deliberate, and could have been avoided.
"We lost Perez for a while with an ankle injury. Hopefully he will recover but I think it will be six-eight weeks out," Wenger told reporters. However, we have (Olivier) Giroud back, Aaron Ramsey will be in the squad.
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The Gunners boss continued, "Very frustrating - he (Perez) worked very hard to get there. He's absolutely gutted, it's an injury that came from nowhere. A stupid one - a deliberate kick. We have a few uncertainties about (Theo) Walcott, (Nacho) Monreal, (Santi) Cazorla. All tests today."
Along with rivals Tottenham Hotspur, Arsenal are unbeaten on their road travels in the league, but Wenger urged caution against bottom-placed Sunderland, whom he believes are better than current form suggests.
"Their main danger is (Jermain) Defoe, and they are good on set-pieces with (Wahbi) Khazri. They are dangerous on set-pieces," the French manager added. "Overall they are a team who is in a bad position but it's very tight at the top and very tight at the bottom."
Arsenal are second in the standings, behind leaders Manchester City on goal difference.
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