The remaining players and others brought in would perform better in the third-tier Western Premiership, he said.
Club president Brian Hickling said, in addition to the defections, they had spoken to Kerfoot and "agreed with him not to continue his tenure as first team coach", ending Kerfoot's time with the squad without a game being played.
"The squad will be managed instead by two club stalwarts, Peter Flood and Tim Hayes, who will be focusing on developing strength and quality in the players at the top level."
Kerfoot, who did strength training with the 2014 team and was asked by the players to put his hand up to coach, said the departures led to a snowball effect where 11 of the 16 have moved on.
Having experienced similar disappointment when the Wanganui United team was disbanded in 2011, Kerfoot said it was "untenable" to keep coaching and he parted with Athletic on good terms to return to guiding the Wanganui High School team.
"There was not even enough players during the early part, that made have changed now, where there was 6-10 players to training.
"I want to coach footballers, and the opportunity wasn't there to do that."
It is a similar story to the start of 2014, when Bryan Mackie took over and then left the coaching role before the season kick off.
The senior Athletic players, specifically Troy Smith with his national league experience, took over coaching themselves and saw off rivals Team Taranaki to win the Federation League, although they were then well beaten in the Central League qualifiers by Wellington Stop Out.
"It was brilliant," said Cronin.
"The squad was running thin - if we'd had injuries it might have affected the team, but they managed to hold it together."
Hickling said the chance to play Central League was "too great a temptation" for those key players.
"We still intend to bolster the squad with at least two Englishmen, who will be here in early April."
The players will come from the professional-based academy in Surrey, following in the footsteps of Joe Thomas and Liam Robinson, who played here last year.
"We want this relationship to work for our long-term plans for football in the city," said Hickling.
"We have set some exciting goals to develop the game here over the next few years that involve our whole club.
"We believe these plans will change the way football is structured in Wanganui for the better."
Wanganui Chronicle football columnist Jason King said the issue had been Athletic trying to run a Central League-calibre team without a development squad at Western Premiership level as backup.
"It's like building a Sky Tower on quicksand. The players may have felt the structure was not in place."
The Wanganui City club have also been consolidating as the 2014 Western Premiership winners come up to the Federation League this year.
Behind the City firsts squad, two more City teams have been raised to compete in the Western Premiership level.
Wanganui Athletic will retain three senior men's teams and a women's team in the local competition.
The season kicks off at Easter.