John Terry has flung his support behind the Chelsea manager, Carlo Ancelotti, and urged his team-mates to "man up and take responsibility" to ensure their season does not peter out in a "disastrous" failure to qualify for the Champions League.

The reigning league champions, eliminated from the FA Cup and a distant 12 points from Manchester United in the title race, confront FC Copenhagen at the Parken Stadium on Tuesday with pressure intensifying on Ancelotti to revive a campaign that has nosedived spectacularly in the past three months. The Italian defiantly warned that Chelsea were very much "still alive", with Terry's public show of support an apparent plea to the owner, Roman Abramovich, not to dismiss the manager in the summer.

"All the players, and everyone involved in the club, have called for stability and we've got that with Carlo," said Terry, who has worked under seven coaches at the club. "He's a great guy, a great manager. The players are 100% behind the manager. He's got complete confidence in us, and we do with him. We know we've underachieved, but this team still has its hunger and its desire. We missed out on the Premier League for three years when United won it, but that's what I lose sleep over: watching other clubs lift trophies.

"It's been difficult in this run. At times we've shown our quality, and we picked up good away wins at Bolton and Sunderland recently and thought that was a turning point. If we'd beaten Liverpool we could have gone on a good run and got back into it, but that didn't happen. Now we have to man up and, as a group of players, take responsibility. It needs to happen now. We've had bad times before and we've always come out the other end, so we aim to stay together as a team and start winning."

Ancelotti, whose contract at Stamford Bridge runs until the summer of 2012, has cut an isolated figure at times over recent months, shorn of his assistant Ray Wilkins in November and unable to arrest a decline that has resulted in five wins in the team's past 16 matches. Terry admitted Wilkins had been "a massive asset to the club who brought a lot to us, and was brilliant at what he did", though he rejected suggestions that his abrupt departure had served to destabilise the players.

The Champions League has been left as his team's most credible route to silverware though Ancelotti – who will start his £50m forward Fernando Torres – retains hope that the campaign could yet end in triumph. He endured similar difficulties at Milan in 2007 when he finished 36 points behind the champions, Internazionale, but claimed the European Cup in Athens at Liverpool's expense.

"This season is not finished," he said. "I've coped with moments like this before. In 2007 it was the same situation, so I should remind you that this could still be the best season that we have had in memory. Maybe it could, alternatively, be the worst. Chelsea has not died. It's still alive."

If the Italian is to breathe life back into his tenure as manager, this team must revive and progress beyond Copenhagen in the Champions League and recover their poise at home to secure a top-four finish. Tottenham Hotspur travel to Blackpool on Tuesday with Chelsea, now fifth, aware they could be five points adrift of the top four by the time they entertain United next Tuesday.

"The worst thing is looking at Spurs and [Manchester] City and seeing them playing well and picking up points," said Terry. "It would be disastrous if we didn't qualify for the Champions League. It's hard to get my head around that possibility even thinking about it now. But, as the manager says, this season is not over. Even if we lost to United on Tuesday, we'd have to think about finishing in the top three.

"We aimed to retain the trophies we'd won last season, but maybe us being knocked out of the FA Cup and behind in the title race could be a blessing in disguise when it comes to the Champions League. We're determined enough. This is our main focus now."

Copenhagen will be awkward opponents despite not having played a competitive match since their final group game against Panathinaikos in December. They retired for the Danish midwinter break 19 points clear at the top of their domestic league and were arguably unfortunate only to draw with Barcelona here in November.