France Under-21 striker Sanogo did not manage to find the net in any of his 14 appearances last season, when he had joined from Auxerre on a free transfer and saw his progress hampered by a back problem.
But, as £30million summer signing Alexis Sanchez watched from the bench, Sanogo produced a clinical display as he scored four times while Costa Rica forward Joel Campbell, back from a loan spell at Olympiacos, also impressed, scoring his first goal in an Arsenal shirt to suggest Wenger already has plenty of attacking options rather than needing to spend big again to find support for lead frontman Olivier Giroud
"Football always surprises you, not only you but me as well," said Wenger, who had drawn a lot of criticism for standing by Sanogo, the striker starting a crucial Champions League clash against Bayern Munich and also the FA Cup semi-final against Wigan at Wembley.
"They need to play of course, but they need to play here.
"Sanogo came last year on a free and we worked very hard for six months with him and from January onwards he was slowly getting better, now that we have worked very hard with him, we want him to stay here.
"Sanogo was injured for basically two years before he came to us
If you look at his goalscoring record before he got injured, it is quite frightening
For a while when he came back last season, he could not score
You could see when he scored the first goal today, suddenly they can rain in.
"He has a big future here, of course, he is 21."
Wenger added: "Campbell has done very well
I like the way he plays.
"He is good on the ball, creative and collectively as well he has a good balance between individual skill and collective attitude - that's not easy to find and there is no reason to let him go
Sanchez came on for a late cameo and is expected to start against Monaco on Sunday.
The arrival of the Chile forward from Barcelona after the World Cup was just one of several signings by Arsenal this summer, with France defender Mathieu Debuchy among the substitutes on Saturday, while teenager Calum Chambers, bought from Southampton for £16million, produced a composed display at centre-back.
Arsenal are expected to further strengthen ahead of the end of the transfer window, and had been heavily linked with Real Madrid's World Cup-winning midfielder Khedira.
While reports of a £30million bid may be somewhat premature, Wenger did not flatly deny any interest when pressed in his post-match media conference.
Asked if Arsenal had enquired about Khedira's availability, Wenger responded
"What is enquire for you?"
The Gunners boss was then asked if he thought the player was available, to which he replied with a smile before leaving
"I don't know
If I read the newspapers, he is available
Source : PA