Shaan Stuart and Will King will be out for the first third of the season at minimum, with Stuart in America and King recovering from an ankle injury.
Another huge loss for the side is box-to-box midfielder Martyn Freestone, who brought a workman-like attitude that complemented the rest of the team beautifully.
Although those key players were missing, von Kwiatkowski said others had stepped up and they could not worry about what had happened.
"We don't have to fear anything. We just have to focus on our commitment and consistency. The first game this weekend will show us where we are at mentally."
New additions to the squad include Neihana Khal and two Wellingtonians - Lukas Bayliss and Matt Bouzaid.
Von Kwiatkowski isn't thinking about title aspirations just yet, rather focusing on games week to week and building into the season as players return from various injuries.
"Just because we did well last season doesn't mean we will go through teams like a hot knife through butter. No opponents will be underestimated."
Versatile Wanganui City FC will continue to ply their trade in the YORB Horizons Premiership after dropping points in only two games all last season.
But, like Athletic, mass changes across the club have forced them to adjust and adapt.
Long-time City influence Kelvin Francis has moved on from the top job, with Mark Hetherington taking over the reins.
Without the likes of Kyle Graham and Eli Fleming for the coming season, a number of youngsters will fill pivotal roles for the side.
Hetherington said the key to the 2021 season was building up their young players and depth for a potential push for the Central Federation League in the coming years.
"It's a very young team. The youngest player I have is 15 and I've got three players in their late 20s and early 30s. The rest are basically Whanganui under-19s.
"I would say we would be in the Western Prem for the next two years. Just to rebuild and get this young team together and hop into Federation and be competitive."
Those seniors include Latham Berry, Anthony Bell and Cameron Hussey, who all bring vast experience and leadership to the young team.
Another experienced player, Jack Jonas, is acting as the interim manager as he recovers from a knee injury suffered last season.
Hetherington isn't putting too much pressure on his side to defend their title, instead focusing on building a strong foundation and developing the side's younger players.
Whanganui Athletic face Levin on Saturday at 2.45pm, with Wanganui City opening the show against Massey University 1sts at 12.30pm at Wembley Park.