Referee Andre Marriner admits he has agonised over the blunder that saw him wrongly dismiss Arsenal defender Kieran Gibbs on Saturday, as he prepares to take charge of Saints tomorrow.
When Alex Oxlade-Chamberlain handled the ball in the penalty area in the 15th minute of the Gunners' 6-0 defeat to Chelsea at Stamford Bridge, Marriner incorrectly showed left-back Gibbs a red card.
He apologised following the game, before the Football Association rescinded the red card and decided against punishing Oxlade-Chamberlain.
Marriner will officiate the meeting between Saints and Newcastle this weekend, but admits he has analysed the mistake he made in west London ''to death'' this week.
Speaking to the Telegraph, he said: ''It knocks you for six to be honest. There's a lot of talk out there that referees make decisions, go home and don't care about it, but that's so far from the truth.
''You're continuously playing the incident over in your mind. You think about how you could've arrived at the right decision and 'what could I have done differently?'.
''You draw from all these other different sorts of aspects to try and find the reasons why you've made a mistake but equally the best thing you can do is try to park it and move on because this incident happened in the 15th minute of the game.
''Afterwards, I analysed it to death.''
The 43-year-old has received support from his colleagues within the Select Group of Referees and from the Professional Game Match Officials' Limited (PGMOL).
Ahead of his return to top-flight officiating at St Mary's on Saturday afternoon, Marriner hopes he has got his ''mojo'' back following a week to forget.
''I made a high-profile mistake last weekend but it's like a player who misses a penalty or a goalkeeper who fails to make an easy save, you want to get back out there the week after to put those demons right,'' Marriner added.
''I'm delighted by the (PGMOL) decision, it shows what my bosses think of me as a referee and hopefully I won't let them down and I'll be able to go out on Saturday and perform at my usual high standard.
''I've met all my colleagues this week, so I've received a little bit of banter from them, which has been good natured. I've been down in the dumps and it's made me smile and hopefully I've got my mojo back.''
The incident has sparked fresh calls for the introduction of video replays to the touchline, from which fourth officials could help the match referee make a more informed decision.
But Premier League chief executive Richard Scudamore believes that, because such mishaps occur so infrequently, there is no urgent need to overhaul the current application of technology.
He told Sky Sports News: ''I think there's a discussion to be had about where you can use it for purely factual matters.
''Last weekend's incident - I won't try to minimise it - was a once-in-every-23-years type of occurrence and I've never even seen a defender throw himself at a shot and make such a good save.
''It was literally so close and right behind the goalkeeper.
''The first thing is that it happens so rarely and the second is that, if one of the fourth officials had taken more time over the decision, things might have come out differently.''