A goal from Jamie Guy put Oxford in the driving seat as they led 1-0 against Sudbury at half-time of their FA Trophy first-round tie at King's Stadium.
Guy, who has hit form since Jim Smith replaced Darren Patterson as boss, took advantage of slip from Haynes-Brown before finishing coolly past Darren Gould.
United should have been ahead on ten minutes, but james constable but blasted over.
minutes later, keeper darren gould made a great punch clear.
then haynes-brown made a brilliant blockk to deny Guy as he went through on goal.
gould was called into action on 17 mins when he held matt day's powerful shot at the second attempt.
guy gave oxford the lead on 30 minutes when he fastened onto a mistake by Haynes brown before finishing well.
Guy almost got a secon, but his header hit the stantion.
A couple of minutes later, Sudbury should have levelled, but David Chick failed to get any power behind his shot.
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