The Baton Rouge Police Department said there were inconsistencies in the account from the student-athlete.
"Due to several inconsistencies in the victim's narrative/disclosures and a lack of cooperation concerning evidence and further interview there was no probable cause for arrest found at this time," Sgt. McKneely told TMZ.
TMZ reached out to the student-athlete, who "says it's the police who aren't cooperating with her."
TMZ also initially reported the investigation, noting Phillips and the female student reportedly had a previous relationship that ended prior to the alleged June 11 sexual assault.
"It's not true and I didn't do it," the incoming freshman said of the allegation, per Sam Spiegelman of SEC Country.
Per Scout.com, Phillips was a 4-star recruit considered the No. 5 inside linebacker in the country and No. 91 player overall in the 2017 class.
He enrolled in the school in June and is expected to make an early impact on the field for the Tigers.