Ighalo attracted the interest of a host of big clubs - and was the subject of a Â£37.5million bid from Chinese club Shanghai SIPG in the summer - after scoring 13 Premier League goals before the turn of the year last season
But the 27-year-old Nigeria international found the back of the net on just two occasions in the second half of Watford's campaign, and he has scored just once in the league this term
Boss Mazzarri changed his formation following Watford's 6-1 thrashing at Liverpool on November 6, and Ighalo was dropped to the bench for the ensuing matches against Leicester and Stoke
But speaking ahead of his side's trip to West Brom on Saturday, the Italian insisted he does not want Ighalo to leave the club when the transfer window opens next month
"I speak about what I know and I speak about what I have seen so far this season," Mazzarri said
"He is a player that I like and I trust very much
"When he was in a good condition at the beginning of the year he played, and started the games
Of course he is a player that we need
"He is in competition at the same level with all the other strikers, and if we want to grow as a club and in the future go further in competitions, then you need to have at least six important strikers and Ighalo is one of them."
Mazzarri's side head to the Hawthorns following a disappointing 1-0 defeat against Stoke at Vicarage Road
Watford spent much of the game trailing through a Heurelho Gomes own goal before they were reduced to 10 men after defender Miguel Britos was sent off in the closing stages
A disappointed Mazzarri stormed down the tunnel at the final whistle without shaking Stoke manager Mark Hughes' hand
"I don't want people to continue talking about things that have little do with football," said Mazzarri when asked about the incident
"It was a nervous game and at the end we got a red card in the exact moment where we were pushing Stoke for a goal
"I went inside in order to avoid the referee, and you can ask Mark Hughes, I went to his dressing room and I gave him my hand there."
Source : PA