Eddie Howe said Fabian Schar was conned by what Alan Shearer labelled Ben Brereton Diaz's dirty tricks during the headbutt incident that saw the Newcastle defender sent off and tempers later flare in a tunnel fracas.
Shearer called it 's***housery at its finest' when Southampton debutant Brereton Diaz fell to the ground after he and Schar nudged foreheads during a first-half altercation. Craig Pawson sent off Schar and booked Brereton Diaz, who was mercilessly booed thereafter.
Newcastle defender Dan Burn then waited in the tunnel for the forward at half-time and Southampton's players were forced to step in.
Speaking after his side's 1-0 win, Howe said: 'I think it's really harsh on Fabby, although I think we all know that you can't give the referee the possibility to even give the red card. It looks like he has been caught by a well-managed situation. It's something we'll learn from.'
10-man Newcastle took the lead through Joelinton in first-half injury-time and held on for an opening-day three points in the second half.
Fabian Schar's first game of the season lasted just 28 minutes as he was sent off for a headbutt
Schar reacted angrily to being shoved to the floor, first pushing Ben Brereton Diaz and then putting his forehead forward
Eddie Howe suggested his Newcastle defender was duped by a 'well-managed' situation
Newcastle icon Alan Shearer responded to the incident describing it as 's***housery'
Howe added: 'In a strange way for us, the red card was a turning point negatively in terms of control, but a turning point in terms of getting the crowd in the game. They felt an injustice. Without that support it's probably a different result.'
Howe said he and the club will review the red card before deciding whether to appeal a three-game ban, but Saints boss Russell Martin believed the dismissal was fair.
'When he (Brereton Diaz) stands still and then (Schar) leans with his head, you give someone the opportunity to make the most of it,' he said. 'It's a moment of madness from their player. I'm sure their players would have done the same (as Brereton Diaz). VAR have seen it back and it has to be a red card.'
The incident caused tempers to flare among both sets of players, first on the pitch and later in the tunnel.
Schar was shoved to the floor from behind and reacted angrily, first pushing Diaz and then putting his forehead forward before the Saints star fell theatrically.
As a large group of players quickly surrounded the scene, Brereton Diaz continued to writhe around on the ground as the Newcastle defender gestured for him to get up.
Fellow centre back Dan Burn even appeared to try to lift the striker up as Magpies goalkeeper Nick Pope and Southampton centre forward Adam Armstrong also intervened.
And despite a VAR check, Newcastle were reduced to 10 men to put their start to the season under threat.
A scuffle ensued as Newcastle players reacted angrily to the decision as they faced going down to 10 men
Tempers flared once again in the tunnel at half-time as Dan Burn and Jan Bednarek clashed
A Premier League statement said: 'The referee issued a red card to Schar for violent conduct. VAR checked and confirmed the referee's call.'
The centre-back now faces a three-match ban after the straight red card, leaving manager Eddie Howe scratching around for reinforcements at the back.
And it comes at the worst possible time for Newcastle with the side already locked in negotiations for Crystal Palace defender Marc Guehi.
On Friday it was reported that Palace are set to reject an initial £60million offer from Newcastle for Marc Guehi.
Mail Sport first revealed the news that the Magpies had submitted their fourth offer for the England international on Friday morning.
But sources close to the deal are indicating that the package is still not suitable for Palace.
It is understood the latest offer comprises of a guaranteed £60million plus a further £5million in add-ons.
Palace want a minimum £65million for Guehi and it appears chairman Steve Parish is demanding that amount in guaranteed money, excluding additional bonuses, meaning Newcastle face paying closer to £70million to complete the transfer.
Eddie Howe said of the bid after the game: 'The conditions have to be right for us. We can't do something that goes against the longer term good of the football club.
'We will try to make the right decision.'
Newcastle have been on the hunt for defensive reinforcements, including Marc Guehi (pictured)
Despite the early setback, the Magpies managed to clinch a winning goal on the strroke of half time through Joelinton
Magpies players, including Bruno Guimaraes (left), were left fuming after Craig Pawson (right) sent off their centre-back
The defender now faces a three-match ban after the straight red card, leaving manager Howe scratching around for reinforcements at the back
Despite the early setback, the Magpies managed to clinch an opening goal on the strroke of half time through Joelinton to take the lead against the newly-promoted side.
Saints keeper Alex McCarthy made a huge error by passing the ball straight to Newcastle striker Alexander Isak, who then knocked the ball to the Brazilian who stroked it home.
After the half time whistle was blown, a number of players clashed in the St James's Park tunnel but the fracas did not last long.
The scuffle during the break appeared to start with Southampton's Jan Bednarek waiting for a group of Newcastle players and shouting some words at Burn.
The centre backs then lock horns as other teammates, including Brereton Diaz, pass the pair in the tunnel.