The North East club find themselves 16th in the table and just two points clear of the relegation zone with nine games remaining, as they take on fellow strugglers Southampton at home on Saturday.
Speaking ahead of the game, Benitez reflected on their "disappointing" season so far although he did say he has a "good team with a lack of experience".
"I think we deserved to win some games and maybe managing them in another way, the last 10-15 minutes, it could be different.
"Against Bournemouth (a 2-2 draw having been 2-0 up) we were really good going forward, Burnley was the same (late equaliser conceded), and we have to manage better this advantage."
When asked whether the match against Southampton was their biggest of the season, the Spaniard replied: "I think you will ask me the same question, maybe against Huddersfield (the next league game).
"Every game is important for us. This is obviously the most important, because it is the next one.
"The difference between top sides and other teams is massive so everything has to be perfect to get points [against top sides].
"When you play teams around you, even making mistakes sometimes you can win, so hopefully we can [on Saturday]. Until the end we have to keep going. Every game for us is a final now."