Fowler and Luik suffered mild concussions in separate incidents during Tuesday's training, while Kerr, the team's leading scorer with 63 goals, has a calf injury that kept her out of Australia's 1-0 win over Ireland in their opening game. She will be re-evaluated after the Nigeria game.
"Morale is high. There's not too much I need to do to be honest, I think everyone's very focused," said Catley, who scored the lone goal on a penalty versus Ireland. "Everyone knows we need to keep the morale high.
"(Injuries) are not what you want ever in a tournament and, in particular, this tournament...as Australian players probably the biggest moment of our careers. But it's football and it happens to every single footballer on the entire planet.
"It's about how the rest of the squad bounces back and performs in a high-pressure situation in the biggest games."
Fowler replaced Kerr in the attack for the Ireland match at Sydney's Stadium Australia, while Luik was an unused substitute. Football Australia said both had fully recovered and started the "return to play" protocols.
That suggests they would be available for Australia's final group match against Olympic champions Canada in Melbourne next Monday.
"When it's concussion protocol as a coach, you have to have the biggest respect for a player's health and if a player is ruled out, they're ruled out," said coach Tony Gustavsson.
"Two days out you always have high intensity (at training). We were unlucky. Unfortunately, two head knocks."
Gustavsson said there will likely be no update on Kerr until Sunday, the eve of the Canada game.
