Eddie Howe has urged Newcastle to express themselves in their "season-defining game" against Southampton on Tuesday as they seek to reach the League Cup final for the first time in nearly half a century.
The Magpies, who have not won a major domestic trophy since 1955, are 1-0 up after last week's first leg, thanks to a goal from Brazilian forward Joelinton.
Howe's men have only lost two matches all season but he said the job was not yet done, even though Newcastle are firm favourites to progress to next month's final at Wembley.
"You have to look at it as an independent game," he said on Monday. "Yes, we have a 1-0 lead, but if you focus on that too much before the game or that becomes part of your psychology, then you're in trouble.
"You go into protection mode and we don't want that. We want to express ourselves in the game and we have to look at it as a league game.
"We're a game away from a final, which would be an amazing moment for us, but we haven't achieved it yet and we've got a lot of work to do to get there, so it's about staying in the moment, not getting ahead of ourselves."
New signing Anthony Gordon will be in the stands at St James' Park as Newcastle attempt to reach a first League Cup final for 47 years.
The 21-year-old forward completed his transfer from Everton, which could eventually cost Newcastle £45 million ($56 million), on Sunday.
"It will be a really useful experience for him tomorrow to sample the atmosphere," said Howe. "It's totally different when you're watching from the stands than it is to playing and feeling it on the pitch, but it will give him an idea of what's in store for him.
"It is going to be potentially a season-defining game, although we are not trying to focus on it that way."
Howe, who hopes to strike a deal for West Ham full-back Harrison Ashby, said he has no intention of allowing Allan Saint-Maximin to leave the club during the January transfer window following Gordon's arrival.
Southampton boss Nathan Jones said his team, who beat Manchester City in the previous round, would not be short of confidence, even though they are trailing in the tie and are bottom of the Premier League.
"With the greatest respect, it (1-0) is an advantage but it can be a tricky advantage," he said at his own pre-match press conference.
"We have to do things right and make sure we start positively, and be our best. We'll be aggressive, we want to go after the tie and we'd really like to get the first goal.
"If we can get the first goal then a lot of things can change, and a lot of things will change."