Mark Hughes feared surrendering a two-goal lead in last season's home defeat to Chelsea had dealt a "mortal blow" to Southampton's hopes of Premier League survival.
Struggling Saints were cruising towards a valuable victory in April before a late capitulation saw them concede three times in the final 20 minutes.
The 3-2 loss left the south-coast club five points from safety with five games to play.
Chelsea return to St Mary's on Sunday and Southampton manager Hughes now believes the setback gave his players the necessary belief to avoid relegation.
"It was huge disappointment at the time, because it was a significant game at the time, we'd got ourselves in a winning position," he said.
"We were in a predicament at the bottom of the table and we needed every point that we could get.
"It was a feeling that it would maybe be a mortal blow but actually it galvanised us and from that point onwards we felt we've just gone up against a very good Chelsea team and should have beaten them.
"We weren't able to but the confidence that we took from performing as well as did against them helped us in the games we faced from then until the end of the season.
"There's no doubt whatsoever in my mind that, even though we might have won the game, we would have got the same kind of reaction from that game in terms of positivity because we needed to convince ourselves that we were a good team and I think we did on that day."
_______________
Read more:
Ian Hawkey: Liverpool's Fab Three look a phantom of the force that 'scared' Manchester City
Premier League predictions: Liverpool beat Man City to go top
Chelsea manager Sarri to work with Loftus-Cheek over international break to 'improve
_______________
Saints have a dreadful recent record in front of their own fans, winning just four of their last 27 league fixtures at St Mary's.
Hughes admits the home form must improve to avoid a repeat of the problems experienced during the last campaign.
However, the Welshman - who has won one of six home matches since replacing the sacked Mauricio Pellegrino in March - feels it is unfair to judge his personal record too harshly.
"I haven't been in charge of too many home games, if I'm honest. I've played 19 games I think since I got this job and only six of them have been at home," he said.
"After the weekend, two of them were against Chelsea and one of them was against Man City, so the opportunities to get actually maximum points haven't been too great, albeit in the other games we should have picked up more points than we did.
"The facts of it is we haven't won too many home games in my time, I think it needs to be mitigated a little bit because we forever seem to be on the road.
"We need to improve our home form because that's going to be a factor in determining what kind of season we have."