On the night he equalled former Manchester United manager Alex Ferguson’s record of overseeing 810 Premier League games, Wenger watched the brilliant Sanchez turn an exciting match with two superb second-half goals in the space of four minutes.
Shkodran Mustafi had given the dominant visitors a deserved lead after 25 minutes but Arsenal were made to rue a host of first-half near-misses as Palace roared back soon after the break with a well-worked Andros Townsend goal.
Then Sanchez, whose future at Arsenal remains uncertain, demonstrated his world-class talent, first with a thunderous 62nd minute snap shot and then a lovely piece of control and fine finish from Jack Wilshere’s long, precise through ball.
Despite James Tomkins ensuring a nervy finish for the visitors with an 89th minute headed goal, the win left Arsenal still in sixth place but they moved on to 37 points, alongside Tottenham Hotspur and to within a point of the top four.
Palace, beaten for the first time in nine games, are 16th on 18 points, just a point above the relegation zone.
There must have been much satisfaction for Wenger, whose own future at Arsenal had never been more hotly debated than when his side lost this same fixture 3-0 at Selhurst Park in April last season.
That defeat inspired the Gunners’ successful run which ended with an FA Cup triumph and Wenger will now be hoping this victory could start another impressive sequence at the start of 2018 as they chase Champions League football for next season.
What part Sanchez will play for him remains unclear but the Chilean, whose name has been consistently linked with a move to leaders Manchester City, could not be faulted and neither, naturally, could his skill.
After Townsend’s well-worked equaliser assisted by a pinpoint Wilfried Zaha cross had changed the game’s complexion, Arsenal’s nerves were settled only when Palace striker Christian Benteke hit a poor clearance out of defence, a mistake that ended with Sanchez rifling home the visitors’ second in the 62nd minute.
Then Wilshere, back to something near his best, picked out a delightful over-the-top, quarterback-style pass that Sanchez controlled expertly on his thigh, before sliding the ball past Palace keeper Julian Speroni.
Sanchez’s excellence prompted the inevitable question to Wenger afterwards about whether he was fearful of losing the Chilean, especially with the striker’s contract expiring at the end of the season.
“I am not fearful but that will be a subject that arises because of his contractual situation,” Wenger told Sky Sports.
”Overall it was a convincing win even though in the second half it was harder than the first. We found the resources to score two great goals and from then we never gave up.
“We have come here and it is a difficult game for everyone in the league. We suffered a bit but for the biggest part of the game we played well.”
Still, Palace, who have become a completely different proposition since Roy Hodgson took charge with them languishing at the foot of the table, pressed to the end with Tomkins’ header ensuring a frantic finish.
“We showed we are a good team and we have quality players in our team. For us, it is a question of keeping fighting. Even at 3-1 down to a team of this quality, there was no resignation or sign of not doing the right things,” Hodgson said.
“Had the game been five or six minutes longer, maybe we could have got something.”
Meanwhile, Arsene Wenger offered a stirring defence of Alexis Sanchez’s attitude on Thursday, insisting the unsettled striker’s match-winning double in the 3-2 win at Crystal Palace demonstrated his continued commitment to the club.
The Chilean, who has been widely accused of not pulling his weight for Arsenal in the final year of a contract which expires next June, produced one of his best performances of the season with intriguing timing.
Wenger told reporters afterwards he was not “fearful” that Sanchez, whose second-half brace in the space of just four minutes turned the game, would leave in next month’s transfer window.
Yet the fact that he should be back to his world-class best with the January market about to open was bound to raise eyebrows.
Manchester City, the Premier League’s runaway leaders, have been consistently linked with a move for Sanchez but, coming into the final six months of his contract, they could wait until the summer to snap him up on a free transfer.
The more cynical of Arsenal’s fans, quick to make their views known on social media after the game, saw Sanchez’s performance, full of commitment and skill, as a shop window display for City‘s, or even Paris St Germain‘s, delectation.
Wenger, though, told reporters: ”Always when people don’t have long contracts, they are questioned. The best way to show they are committed is to give that kind of performance.
“I felt he was very good tonight from the first minute on, focused on the game. This kind of Sanchez is a great football player, as we know. That’s the kind of performance we want from him.”
Though it has been considered a formality that Sanchez will leave, Wenger added: ”Look, first of all nobody knows what will happen really. It’s difficult to speculate.
”At the moment we are focused on the next game, with the players committed and ready to fight. It’s not a guarantee of how long you stay somewhere.
“As long as you are somewhere, you give your best. I‘m not a specialist in psychology.”
Jack Wilshere, also outstanding in the Arsenal win and creator of Sanchez’s second goal with an exquisite long pass, said afterwards that he expected to sign a new deal with the club.
The England midfielder, who like Sanchez is out of contract in the summer, said: “The boss said he will speak to me...I‘m sure it will get done.”