Today's 1-0 win over Manchester United means that a positive result against Spurs will book Chelsea's place in Europe's top competition with two matches of the campaign to spare.
Speaking after the victory over United, Benitez told BBC Sport: "It's an important win. We knew we needed to win a couple of games and this is the first one.
"If we can beat Tottenham on Wednesday, we will be in the top four with two games left to play."
After Tottenham, Chelsea will still have Aston Villa and Everton to play.