Davenport, a former England under-21 international, was left with a 15-inch scar on his leg after the attack in August. He returned to light training recently.
Worrell Whitehurst, the boyfriend of Davenport's sister, Cara, admitted causing grievous bodily harm with intent at Luton Crown Court, the Press Association reported.
The 25-year-old from Derby also pleaded guilty to unlawfully wounding Davenport's mother, Kim Stupple, during the incident in Bedford, 50 miles north of London.
Whitehurst will be sentenced at a later date.
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