Italy, who last went through a World Cup qualifying playoff in 1998 when they beat Russia 2-1 on aggregate, must beat Sweden over two legs to qualify for next year’s tournament and their lacklustre recent performances have many fans fearing the worst.
The 69-year-old Ventura, Italy's oldest coach, was in confident mood on Monday.
"It's an important moment for my and for my career, and also for the players because some have the chance to start a new cycle and others to finish one," he told reporters.
"Going to the World Cup is important for everyone, the young and the not-so-young.
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"But I'm in a relaxed frame of mind because I have the goodwill of the players and because Italy has always come together to face these challenges - you just have to look at the 65,000 tickets sold for San Siro."
"I have never considered the possibility of not going to the World Cup,” he added. "Italy has never let us down and we won't let Italy down."
Italy, who last missed the World Cup in 1958, visit Sweden for the first leg on Friday and host the return three days later in Milan.
The four-times world champions finished second in their qualifying group behind Spain and their confidence was undermined by September's 3-0 defeat in Madrid.
“Before the Spain game, we had a good run of wins and many good games. After that game, due to the manner of the defeat, a lot of criticism came our way," Ventura said.
Brazil-born midfielder Jorginho was a surprise inclusion in the squad, the first time the Napoli player has been called up since Ventura took over following Euro 2016.
Ventura refuted the suggestion that it was an attempt to prevent the 25-year-old choosing to play for Brazil - an option that will be closed once he has played a competitive game for Italy.
"I called up Jorginho because he has been playing well, that's all," he said.
(Reporting by Brian Homewood, editing by Ed Osmond)
