The 41-year-old former Arsenal and England star, who has been married for 17 years and has four children, admitted one charge of having unlawful sexual intercourse with the girl and one of indecently assaulting her in January last year. But he denied two further counts of indecently assaulting her.
The prosecution accepted the not guilty pleas at yesterday's hearing at London's Knightsbridge Crown Court and the case was adjourned until 26 March to await the preparation of reports.
Renewing Rix's bail on condition that he did not contact the girl or her family "either directly or indirectly", Judge Timothy Pontius told him:"The fact that I'm about to release you on bail and the fact that I have ordered a report should not for a moment be taken by you as an indication of the sentence you will ultimately receive.
"Because of the gravity of these offences, I must keep all my sentencing options open and they include, perhaps in the forefront, imprisonment.
Rix, of Richmond, south-west London, who was capped for England 17 times, is regarded as one of the country's top coaches and helps to manage Chelsea's expensive line-up of foreign stars. He is assistant to the former Italian international Gianluca Vialli.
Laura Cobbs, for the prosecution, told the court that Rix's guilty pleas were acceptable to the Crown. It was not intended to proceed with the remaining allegations, which would now "lay on the file".
Desmond de Silva QC, for the defence, told the judge that Rix was of hitherto impeccable character, and added that he felt the court would be assisted by a pre-sentence report in "this exceptional case". The judge agreed and put the case back for five weeks. Rix then left the dock to see a probation officer.
The maximum sentence for having unlawful sex with a girl under 16 is two years and for indecent assault 10 years.Reuse content