James Hunter, 38, appeared at York Crown Court on Monday charged with two counts of sexual activity with the victim.
Hunter, of Tindall Street, Scarborough, pleaded guilty to both counts and even his defence counsel admitted jail was inevitable.
The girl, who cannot be named for legal reasons, fell victim to Hunter between December 2015 and February this year, the court heard.
Hunter’s barrister Taryn Turner said her client knew that jail was inevitable.
“He has been open and frank (about what he had done) and is realistic about the inevitable sentence,” she added.
Mrs Turner made no application for bail and judge Andrew Stubs QC remanded Hunter in jail until sentence on Friday.
Mr Stubbs told the disgraced coach: “I understand that you are realistic in acknowledging that the only decision I have to make is how long your prison sentence will be, because there will be an immediate prison sentence.”