Nketiah, 18, came off the bench and scored twice to lead Arsenal past Norwich City 2-1 after extra time at the Emirates Stadium on Tuesday.
Wenger said he knew the teenager was capable of delivering off the bench against Norwich and was repaid with Nketiah equalising immediately after coming on in the 85th minute.
"I know he has character and is not afraid," Wenger told a news conference.
"He smells the combination movements, he can give and go and once a player has that in his game, they have always a chance.
"The guys who can understand that if they give the ball somewhere and they can get it back and know where to get it back, the quality of reception is a very important quality.
"I would say the quality of the reception, he has that."
Wenger admitted he probably would not have introduced Nketiah if he had more senior options on the bench.
The Frenchman said his change was purely to make Arsenal more dangerous, with Nketiah finding the winner in the 96th minute.
"We lacked ideas, we lacked a little bit to create clear-cut chances," Wenger said.
"I was impressed by the defensive performance of Norwich and so you sit there on the bench and think, 'What can we do to be a bit more dangerous?'
"It was the occasion where we had to take a big gamble because there was not much time to go and I know that Eddie can score a goal."