The Chile international scored Arsenal's crucial second goal in the Premier League victory at Loftus Road.
Having seen the striker's strong start to life in England curtailed by injuries in recent weeks, Wenger was full of praise for Sanchez's determination.
"It's good because when you don't score for seven or eight games it is on your mind, even if you don't say so," the Frenchman explained.
"He took his chance well, he's tricky, had a short back lift and scored a good goal.
"He never gives up and that’s the strength of a good striker as well. He’s resilient and he showed that he has the mental strength to respond."
The hard-fought victory was made all the more important by the fact the remainder of the league's top seven also picked up three points.
Asked about the race for the top four, Wenger added: "It's hot up there because everyone won.
"We can only focus on our performances and keep going. Ten games to go, six at home, four away. We just need to focus on our performances."
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