Burgess Hill 2, St Leonards 0: New St Leonards manager Gary Bowyer refused to be downcast after seeing his side crash out of the Cup in the third round.
The county division one leaders totally outplayed their Dr Martens opponents to set up a quarter-final match against either Arundel or Rye and Iden United.
Two goals within the first five minutes by Steve Harper were enough to win the game but it could have been more.
Bowyer took charge of Saints just an hour before the home defeat by Banbury United on Saturday.
He replaced Terry White, who resigned on Friday after Saints had suffered 12 consecutive league defeats and sunk to second from bottom in the league.
Bowyer said: "I was pleased with the performance to be honest. We were run ragged in the first half-an-hour but after that we began to believe in ourselves and we improved a lot.
"The players have lost so many games and are very young so things are not going to change overnight but if we show some of the passion we did tonight then we will be okay."
The home side dominated from the start and took the lead inside two minutes. Harper received the ball in space on the edge of the area and hit a shot which cannoned off the far post before going in.
Harper doubled his tally three minutes later with a turn and shot from Matt Geard's corner which squirmed under Greg Nessling in the Saints goal.
The Hillians almost increased their advantage on 22 minutes when Richard Carter's angled shot came off a post.
The shell-shocked visitors had to wait until the 33rd minute for their first shot when Liam Baker saw his effort well saved by home keeper Pat Gannon.
The home side started where they left off after the break and almost scored another on 55 minutes when Phil Churchill's powerful shot was palmed over by Nessling.
Ashley Carr went close four minutes later with a curling effort which flashed inches wide. Peter Baker summed up the night for Saints on 70 minutes when his 20 yard shot sailed high over the bar.
Burgess Hill boss Danny Bloor said: "We won it in the first five minutes which is exactly what we wanted to do.
"We said beforehand that we wanted to go at them from the start and really rough them up. It's great to win against sides who are above you because that is where we want to be and gives the players the confidence that they will get there."
Burgess Hill: Gannon, Edwards, Guile, Head, Day, Downey, Harper, Carter, Churchill, Carr, Geard. Subs: Sullivan, Lutwyche, Williams, Kilpartrick, Callaghan.
St Leonards: Nessling, Watson, Matthews, Henty, Ray, Cornelius, Rickett, Bowyer, P. Baker, Pegman, L. Baker. Subs: Scott, Whiteman.
Referee: Dave Phillips (Chichester).
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