It was a night to forget in Madrid on Sunday (AEST) as Italy succumbed to their first qualifying defeat in 56 games.
An Isco brace and a goal from substitute Alvaro Morata condemned Italy to their first loss in a qualifier since 2006 and put Spain in pole position to claim the one and only automatic World Cup berth in Group G.
Italy are three points adrift of leaders Spain and four ahead of Albania after seven matches as a play-off looms, but head coach Ventura is confident his side will be among the 32 teams to feature in Russia.
"When the group was drafted, we knew that for the first time only the winner would qualify," Ventura said ahead of Wednesday morning's visit of fourth-placed Israel.
"Of course, if you're not top seed and you play against Spain, you have to concede that you will probably have to go through the play-offs.
"Actually, that's what almost everyone thought at that time. We did a good job in getting tied to this game. We did not do a good job on Saturday (Sunday AEST), and Spain deserved to win.
"We will go through the play-off, but we're sure that we will qualify for the World Cup.
"I agree with [Italian Football Federation president Carlo] Tavecchio, not going to the World Cup will be very bad.
"But we're not thinking about it now, we're just going to think about the game with Israel, we need to win to qualify for the play-offs."
"When I said that Spain were not human, I meant it because of their qualities," he said.
"You can't buy qualities, either you have them or you have to work hard to improve. But you can't do that in just 20 days.
"I believe that some teams are good and they can play at the same level with great teams just through hard work, otherwise the same team would win all over again.
"I started coaching one year ago and we played France 48 hours later, we had good results since then. Now we played Spain in September.
"I believe if we had played them in November it would have been different. Maybe we would have lost anyway, but we would have been at the same level of preparation.
"Not the same level of qualities, of course. I also believe if we would play Spain at the World Cup, after the right amount of preparation, we would play a different game."
Italy captain Gianluigi Buffon, meanwhile, said: "We need to accept criticism. It's inevitable like the changing of the seasons.
"Personally, I don't feel resentment. We lost 3-0 in a very important game, I'm the goalkeeper and the captain, it's natural to receive criticism.
"The season started too well for me, so it's natural that something now goes wrong. People ask me if I felt hurt by what was said about me, but I honestly don't. This does not affect what I am and what I want to keep being."