The former Nottingham Forest man has been brought into the squad following an injury to fellow defender Taylor Parr last weekend.
The Australian, who operates primarily at right-back, signed a two year deal with Forest in 2019 after impressing while on trial.
He went on to feature for their U18s side before stepping up to the U23s.
Doorbar-Baptist joins a Cambridge side currently mid-table in the Pitching In NPL Midlands Division, 13 points adrift of the play-off places.
Photo credit: Nottingham Forest
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