Walter Mazzarri has warned Watford the threat of relegation still lingers as they prepare to face West Brom on Tuesday night.
Mazzarri's side ended a four-game winless run by beating Sunderland on Saturday and are seven points above the Premier League drop zone in 12th with nine matches of their season remaining.
But Mazzarri insisted Watford were not guaranteed to retain their top-flight status ahead of their latest test against a side fresh from a clean sheet at Old Trafford.
"I try to instil in every player that we need to fight in every game," the Italian said at Sunday's press conference.
"We saw West Brom's quality in the last game against Manchester United. They have many points in the league this season and we must do our best to face them.
"Until the mathematics says we are safe, we are not safe. We need to not think about this and think about the West Brom game."
Miguel Britos' winner at the weekend came from a set-piece but Mazzarri knows Watford will have their work cut out in both boxes on Tuesday.
Jose Mourinho labelled West Brom the best side in the league from dead-ball situations in the build-up to Saturday's goalless draw and Watford were undone twice from set-pieces in their 3-1 defeat at The Hawthorns in December.
"I agree with Mourinho," added Mazzarri.
"They've scored 19 goals from set-pieces. We have to try to be careful not to concede any and, if we do, be careful from them."
Defender Younes Kaboul will miss the midweek clash and his campaign could be over after he sustained a hamstring injury on Saturday.
"We need to assess Younes Kaboul," said Mazzarri.
"With what happened on the pitch, we have a feeling it is going to be a long injury. Maybe out for the season, we do not know yet."
Watford will again be without Christian Kabasele and Ben Watson as they continue their rehabilitation in light training, as well as long-term absentees Mauro Zarate and Roberto Pereyra.
But Troy Deeney and Sebastian Prodl are set to return while Valon Behrami is in contention to make his comeback at Tottenham on Saturday.
"When we play three games, after the first game I look who is the most fit and I mostly concentrate on that," said Mazzarri.
"I might well decide who is going to play on Tuesday after the last session on Tuesday morning. I will speak to various people about who is going to play."