Phoenix’s latest defeat saw them drop to second from bottom in the Midlands Premier table.
Bottom side Oundle, who travel to Castle Park in April, are six points adrift with two games in hand.
However, Phoenix look set to escape relegation with the RFU set to restructure the league format for next season.
Late call-offs due to illness and unavailability meant Phoenix were forced to reshuffle the pack not for the first time this season.
The game started brightly with both teams fighting a strong swirling breeze and, after an early penalty for the home side, Tom O’Brien squared up the game at 3-3 in the first five minutes.
The next 20 minutes were evenly matched but a lack of discipline proved to be Phoenix’s downfall.
Conceding penalties under pressure led to a yellow card for full back Joe Gomes and, while down to 14 men, the visitors conceded two costly converted tries to trail 17-3.
Both teams traded penalties before the interval with O’Brien again slotting home for Phoenix.
Phoenix, back to their full complement, needed to start the second half well but errors whilst in possession lead to a Dudley counter attack and another converted try increased their lead to 27-6.
Phoenix did enjoy good field position and possession but could not convert it into scores against a resolute home defence and Dudley wrapped up the scoring with a fourth converted try.