The 33-year-old believed those responsible had been identified.
Ifill's account was backed up by teammates Alex Smith and Griffin McMaster.
"Unbelievable the things I heard from the bench...it's 2012 people," Smith wrote on Twitter. "I'll leave it for now but I will say it was very racist and disgraceful..."
Back-up goalkeeper McMaster said the abuse Ifill received upon being substituted was not acceptable.
"In addition racist behavior occurred which is unacceptable, then for the alleged people to do a runner #unacceptable," McMaster wrote on Twitter.
Phoenix coach Ricki Herbert would not discuss the allegations after the match.
"It's not for me to confirm or deny, its best to go through that process and talk to Adelaide," he told media. ''There was a few comments that we have shared with the club officials ... with regards to a player."
Football Federation Australia, Adelaide United and police have all been made aware of the incident and are investigating the claims, the Sydney Morning Herald reported.
- nzherald.co.nz