It was Chi’s eighth win in the past nine matches at Oaklands Park – the only defeat coming against Brighton & Hove Albion in the Sussex Senior Cup.
Miles Rutherford & Co gave starts to U23s players Ollie Carroll, Jack Farrier and Charlie Oakwell-Boulton with youngsters Cam Russell, Ollie Barry and Luke Wallis on the bench.
Regulars Kieran Magee, Ryan Davidson, Ben Pashley, Lloyd Rowlatt, Kaleem Haitham and top scorer Callum Overton were rested.
Lewis Hyde returned to the XI for the first time in five weeks and partnered skipper Jamie Horncastle at centre back, with Farrier and Rob Hutchings either side. Oakwell-Boulton joined Ben Mendoza and Dunn in midfield with Prichard and Tyrone Madhani offering an attacking threat, and Scott Jones up top.
The visitors, who ply their trade at the same step of the non-league pyramid but in the Isthmian south central division with the likes of Hanwell Town who Chi knocked out in the previous round, forged a couple of chances early on.
Kai Hamilton-Olise strayed offside in the first of these and Tayshan Hayden-Smith forced Carroll to gather the loose ball when his third minute free kick was only half cleared.
Chichester countered and won a corner which was headed away for another one that Madhani swung in and defenders smuggled away.
Afolabi Soyemi-Oloade beat Farrier in Westfield’s next move, cut inside, and pulled a fine stop out of Carroll to concede a corner with his legs.
Then Prichard gave the hosts the lead with a neat finish into the bottom left hand corner following nice play from Hutchings, Jones, Dunn. Farrier and Mendoza in the build-up.
Westfield play-maker Hayden-Smith gave Caroll something else to think about with another set-piece that the young keeper couldn’t fully control but Jones headed powerfully clear – the referee blowing for an infringement anyway.
Mendoza next took the ball down on his chest and got off a volley that did little to trouble Carroll’s counterpart Callum Blackhurst.
And then Hamilton-Olise levelled less than four minutes after the opener beating Carroll to his right following a super defence splitting pass from Hayden-Smith.
Soyemi-Oloade dragged one wide moments later latching on to another measured ball.
Farrier did well to cut out Hayden-Smith’s pass to Callum Abraham-Barlow before a Mendoza back-heel to Jones didn’t quite come off and Hutchings crashed an effort into a Westfield defender.
A slick passage of play saw Farrier deliver a precise cross on to the head of Jones but the Chi No9 couldn’t steer it in this time.
Kai Davis probed down the right wing and into the area only for a combination of Hyde and Hutchings to block his attempt for a corner which Abraham-Barlow took and Oakwell-Boulton cleared.
Hyde’s excellent tackle denied Soyemi-Oloade on the half hour and Mendoza fired a shot high over the bar after a nice exchange between Farrier and Prichard.
Blackhurst then claimed a deep Madhani cross ahead of Jones.
Prichard, with three goals in two games, wasn’t far off again five minutes before half time when after a bit of pinball it sat up for him, but he pulled his drive wide of the mark.
An odd free kick, and there were a few to be fair, was cleared by Hyde to a Westfield midfielder who skied an effort into the tennis courts.
Dunn had a go at the other end that nicked off an opponent and out for a corner, and then Chi got away with one after a coming together of the Canadian and Hamilton-Olise that might have been a pen on another day.
And in the minute of time added on Oakwell-Boulton did well to hold off Hayden-Smith and let the ball roll back to Carroll.
Russell replaced Horncastle at the break and marshalled the dangerous Hayden-Smith superbly.
Chi got going down the right flank through Farrier who found Jones only for Blackhurst to smother his low cross.
The Westfield keeper then spilled another Jones’ delivery but gathered the ball at the second attempt.
Next, Hutchings steered a Hamilton-Olise cross out for a corner as the game swung this way and that.
Dunn cleared this and then lost the ball, although Farrier, who impressed all evening, bailed him out.
Mendoza picked out Jones with a lovely pass and Chi won another corner which came to nothing.
Russell tried his luck with a long-ranger that was high and wide and Hayden-Smith forced Carroll into a stop with one from a similar distance.
Opportunities came and went for the visitors around the hour mark but Carroll saved smartly; a Hayden-Smith shot was deflected for a corner which was turned away; and Hutchings cleared an attempt off the line.
Both sides rang the changes with Wallis on for Jones for the last 20 or so.
Carroll came out swiftly to clear ahead of Soyemi-Oloade and a Westfield teammate cracked one way over.
Wallis and Hutchings then hooked up and the left back’s cross was inches away from Prichard.
The Chi goal scorer was caught moments later for a free-kick in Madhani range.
Blackhurst palmed this acrobatically out for a corner that Madhani whipped in for Dunn to get a touch of sorts for what would prove to be the winning goal.
Farrier and Wallis combined as the hosts probed once more but Wallis couldn’t get the ball under control in the box.
Hyde then headed a Hutchings set-piece narrowly wide and Madhani’s left footed effort curled over after Russell teed him up.
Wallis struck a fierce shot into Blackhurst’s midriff, while Westfield sub Maciej Tajs had an effort blocked.
And in the last move of the night Barry, who’d come on for Prichard, combined with Wallis only for Blackhurst to claim his low cross.
Chi are back in league action at Lancing on Monday 27th December (Kick Off 3pm).
Chichester – Carroll, Farrier, Hutchings, Horncastle, Mendoza, Hyde, Oakwell-Boulton, Dunn, Jones, Madhani, Prichard. Subs: (Magee, Barry, Pashley, Russell, Wallis)