What's more, he believes the Swans must claim the scalp of a flag contender to have any chance of doing some damage in September.
The Swans have lost to each of the top five teams this year, most recently to Collingwood last Saturday night, but Mattner said he hadn't given up hope.
"We want to play finals football, and we want to be there in September. If we don't beat them now, we're going to have to beat them then. We need to beat them during the year to get some confidence up," he said.
He said the Swans' failure to replicate their early-season performances against the very best teams had cruelled their chances of capitalising on a 5-1 start to the season.
"Against the better teams, you just have to play four quarters of good, solid football, and we haven't done that yet," he said.
"I guess there's that bit of doubt of, 'Can we match it with the top teams?', but I think we can if we play four solid, good quarters of football like we have against some of the lesser teams.
"The better teams put better pressure on; your skill execution has to improve and your pressure has to be better to stop them scoring easily on their turnovers. It's something we've got to work on.
"Having a young team is probably one of the reasons but also the opposition is a lot better, so the whole team has to lift.
"If we do that, we can beat some of those top four sides."
The return of premiership defender Tadhg Kennelly in the summer gave the Swans an embarrassment of riches among their running half-backs, with Mattner, Rhyce Shaw and Nick Malceski also enjoying strong pre-seasons.
Rather than cramping one another's style, Mattner said the quartet was able to take advantage of their similar skills to ensure the Swans always had plenty of creativity from defence.
"Now that all four of us are back, it means that if they tag one or two of us, there are still another couple to run off and create, and be that attacking defensive player," he said.
"We can all play on the wing and even play a bit up forward, too, so the variety of positions we can play has been great."
The Swans' early-season surge was characterised by crisp ball movement off half-back, and Mattner conceded that opposition teams had recently stifled that aspect of their game.
"A lot of teams have been a bit wary of the run through the middle of the ground," he said.
"Our last couple of weeks, we've been focusing on moving the ball quicker and getting it into the forwards quicker. That's probably been the biggest change from earlier in the year.
"We haven't had the consistency with the same forwards every week, so that's probably been the toughest thing. But as a defence, we just want to get the ball forward as quick as we can and give the forwards the best chance one on one."
