The Hornets are currently 17th in the table but have not won a match since their surprise 4-1 victory over Ole Gunnar Solskjaer’s Manchester United on 20 November.
Over a seven-day period starting on Saturday, Watford travel to Newcastle before taking on Burnley and Norwich in a week that could have a significant impact at the bottom of the table.
However, Ranieri believes his side have the quality to remain in the top flight.
“When I say I believe in my team, I saw in the training sessions, they work so hard, and if you continue – with luck – to fight, to believe in yourself, sooner or later you will win. That is important, that is what my experience tells me,” the Italian manager said.
“I say to them (the players) we have to continue, because it is sure, if you come to watch, the training sessions are fantastic. I have a lot of experience and I say this team will be safe. It is unbelievable our position, it’s unbelievable.”
Watford have made three new signings already in January, with midfielder Edo Kayembe arriving from Eupen and defenders Hassane Kamara and Samir joining from Nice and Udinese respectively.
However, since Ranieri took over from Xisco Munoz in October, the Hornets have lost 10 out of 12 matches, and a further defeat at St James’ Park on Saturday would see the club slip into the relegation zone.
“I believe in this team and I’m sure at the end we will be safe,” added Ranieri. “We have to change position. It’s not possible to continue this way.
“But I remember in the last match against Spurs in the Premier League (a 1-0 home defeat), we were focused in that match, we were very solid, and now I have new players, three new signings, and I’m very happy with the team.
“We must stay together and fight in every second of the match. This is a big game for us and for them, but also in this week we play three times against teams in the relegation fight.”
In addition to the new signings who could be in line to feature, Ranieri will be boosted by the return of some injured players, including the influential Emmanuel Dennis, who did not travel with Nigeria to the Africa Cup of Nations.
“He is very important for us,” said Ranieri. “He scored eight goals and has five assists, but he’s important not only in this way, it’s important how he plays for the team. Always I say it’s important to play for the team.”
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