The Chilean, who arrived from Barcelona for around £32m in July, has netted eight goals in 15 appearances this term, and the Gunners manager has been delighted with how quickly he has adapted to the Premier League.
Speaking to the club's official website, Wenger said: "He took advantage of the mistakes [Sunderland] made but he's also got a super quality.
"He's quickly [onto defenders'] feet which is why he wins many balls that normal players don't.
"He's very quick in transition from offence to defence and wins the ball back very quickly. We can take advantage of that."
The Gunners are currently fifth in the Premier League, with 14 points from nine games.