Aaron Ramsey gave Arsenal the lead in the first half at White Hart Lane but the Gunners were reduced to 10 men when Francis Coquelin received a second booking soon after half-time.
Tottenham took the lead after Toby Alderweireld fired home and Harry Kane added a second moments later.
However, Sanchez fired in late on to rescue a point for the 10-man Gunners and keep them to within three points of their bitter local rivals heading into the final nine games of the season.
Speaking at his post-match news conference at White Hart Lane, Wenger said: “He had a great attitude today.
“I hope that will give him needed confidence and encouragement to continue and the goal will give him a lift.
“Certainly, it will give him a bigger a lift now.”
Sanchez missed the busy Christmas period with a hamstring injury.
Arsenal, who are third in the Premier League table, take on Hull City in their FA Cup third-round replay on Tuesday night.
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