Umaga spoke about the wider importance of his team following a 29-14 loss to the New South Wales Waratahs in Sydney on Friday night, an eighth successive defeat for his team, who are last in the standings.
Moana's ownership on Wednesday announced it won't continue funding the side beyond this season due to a lack of commercial support and small crowds.
New Zealand Rugby is hoping another entity will purchase the licence for Moana, which was set up as a pathway for Tongan, Samoan and Cook Island players.
The team has been based in Auckland for its five seasons of existence rather than playing regular games in the Pacific Islands, as planned.
Former All Blacks captain Umaga said disbanding Moana would remove a professional platform for Pasifika players.
"The gap between where we (Samoan and Tongan unions) are currently, internationally, to where we need to get to, is very big," Umaga told reporters.
"Without Moana to bridge that gap, it's going to be tough. If we keep going the way we're going, the possibility is that they might not make the next cycle of the World Cup.
"There's still a glimmer of hope for us and that's what we've got to look forward to and we've just got to keep pushing forward."
Umaga, who will take up a post as All Blacks assistant coach this year, praised his team's on-field efforts following a difficult week.
They led 14-12 at halftime thanks to two tries to scrum-half Melani Matavao, both from quick taps.
The Waratahs dominated the second half, boosted by fullback Sid Harvey's two tries to notch a fourth win from eight games and climb to seventh.
Coach Dan McKellar praised the Waratahs' composure, particularly late in the game after the players were taken from the field in the 70th minute because of a risk of lightning strikes.
The match was delayed for 40 minutes.
"We had a really clear plan around what we needed to do in that last 10 minutes," McKellar said.
"That's probably the most pleasing part is that we were all pretty calm and understood what was required."