Failure to win - or score in - either of their last two Barclays Premier League games has seen the Blues slump back to fifth in the table with 12 matches to go.
Vice-captain Lampard told BBC Sport: "We must finish in the top four and can never take our eye off the ball. It would be a disaster if we didn't qualify."
Chelsea will have to wait to get their faltering league campaign back on track, with their next two games Saturday's FA Cup fourth-round replay against Everton and Tuesday night's Champions League last-16 first leg at FC Copenhagen. With the league all but surrendered - Manchester United are 12 points clear of Chelsea - the cups are now vital, according to Lampard.
The midfielder said: "There's huge importance because you can see the league's going to be difficult and that means it's more important to reach finals."
The 32-year-old also backed £50million man Fernando Torres to come good after the Spaniard flopped in his first two games for his new club.
"He's made a huge difference," Lampard said.
"No, he hasn't scored in two games but all the spotlight is on him. There's a huge responsibility, people are looking to him to do it instantly, but he will make a difference to us.
"He's a top-class player, he has boosted the lads already and for sure will come good, he's going to add to us in a big way.
"David Luiz has come in as well and has been fantastic."
Source: PA
Source: PA