Dan Biggar insists Saints have the belief to become Premiership champions during the next couple of weeks.
The black, green and gold travel to Exeter Chiefs for a play-off semi-final this Saturday (kick-off 4.30pm).
Saints finished fourth during the regular season, 30 points behind the table-topping Chiefs.
But it is now knockout rugby in the bid to make the June 1 grand final at Twickenham, and Wales star Biggar is fully confident in the ability of his team-mates.
"When I first arrived, the club was going through a bit of a transition in terms of a couple of below-par years, but from the moment Chris (Boyd) came in the whole dynamic of the club changed," said Biggar, who joined Saints from Ospreys last summer.
"He brought his winning mentality and belief into the club and that's what the squad needed: that real belief and someone with the experience and knowledge of Chris.
"As the season's gone on, we've been finding out how best to play, what strengths we've got as individuals.
"The table doesn't lie and we've been the fourth-best team in England.
"Now we're in the top four, the question to ask is, 'can we go on and win it from here?'. The answer is yes.
"We're perfectly aware of how difficult the challenge is, to probably have to go and beat Exeter and Sarries two weeks on the bounce, but once you're in the play-offs, it's anybody's game."
Saints were beaten 40-21 by Exeter at Sandy Park on the final day of the regular season last weekend.
But Biggar said: "We've reviewed the game, looked at bits and pieces and what it felt like on the field was that there was very little between the teams in general play.
"They just strangled us a little bit at the set piece, which allowed them to have field position. If you allow any team field position, never mind one that's top of the league, you're going to have a tough time.
"What we can take full confidence from is that in terms of general shape, we caused them no end of problems and we lived with them.
"It's about avoiding that set-piece to set-piece game, which is obviously a major strength of theirs.
"Our strengths are keeping the ball in hand and not feeding the opposition huge amounts.
"We don't want to be getting into a set-piece game. Our set-piece has improved incredibly over the past few months but we're well aware that against the likes of Sarries and Exeter, we're a bit below them.
"That's taking nothing away from where we are, we've got other strengths, but for us to have a chance of winning we need to keep the game fairly open and to play some risk and reward rugby."
Saints are now in their first Premiership play-off semi-final since 2015.
And it will be Biggar's first as a Northampton player, having joined from the Ospreys last summer.
"We've tried to treat this as any other week," the 29-year-old said.
"Especially having played Exeter last weekend, it was almost a little bit of a rehearsal and both teams found out a bit about each other.
"This week has been relaxed and Chris has tried to keep everyone relaxed because you don't want to be too pumped up early in the week.
"It's got a different feel to it when it's a semi-final week and this is one of the reasons I signed for the club.
"This league has been far and away the toughest I've had in my career in terms of having to perform every week and if you don't perform you get found out quickly.
"We were a little bit off it against Gloucester at home and we got put away. We were a little bit off it at Saracens and we got put away.
"This league gives you nothing in terms of margin for error but that's why it's even more rewarding to be in the top four.
"After the first five or six rounds, if everyone's honest there were probably only two play-off spaces to play for.
"The top two were well gone so there were 10 other teams and to finish in two of the spaces outside of the big two is an excellent achievement for a club which is in transition.
"Now we're in that top four, it's a huge opportunity to go out and play some attractive rugby, to play with freedom and to build momentum hopefully going into the following week."