Terry Devlin opened the scoring for the hosts in the 36th minute before Swansea equalised through Zan Vipotnik's 85th-minute penalty. However, Devlin restored Portsmouth's lead in the 92nd minute before substitute Thomas Waddingham sealed the points in the 98th minute.

The match began with Portsmouth pressing for an early breakthrough, as Odin Bailey set up Adrian Segecic inside the penalty area only for the Croatian to miss the target. Swansea were forced into an early tactical change when Stephen Welsh suffered a knee injury following a challenge from Ebou Adams.

Portsmouth continued to apply pressure down the flanks, with long throws from Tyrese Shade causing problems for the Swansea defence. The opening goal arrived when Devlin fed Segecic, whose cross was partially blocked before Devlin reacted quickest to drive a first-time right-footed shot past goalkeeper Lawrence Vigouroux.

Swansea struggled to create clear openings in the first half, though they came close just before the interval when a deflected shot from Melker Widell looped over the crossbar. The visitors made changes at half-time, introducing Elijah Just to add more attacking impetus.

Portsmouth suffered an injury setback in the 54th minute when Iyah Mohamed was forced off with a calf problem and replaced by captain Marlon Pack. The hosts briefly thought they had doubled their lead when a goal was ruled out following a foul in the build-up.

Further disruption hit the home side when a triple substitution saw Adams, Segecic, and an injured Milovanovic replaced by Josh Murphy, Thomas Waddingham, and Abu Kamara. Swansea capitalised on the unsettled period when Regan Poole pulled back Vipotnik inside the area.

Vipotnik converted the resulting penalty past goalkeeper Nicolas Schmid in the 83rd minute to level the score at 1-1. Swansea nearly took the lead shortly after when substitute Ross Stewart hit the crossbar with only the goalkeeper to beat.

Portsmouth responded during five minutes of added time by mounting a furious finish. Following a right-wing corner from Bailey, Stewart cleared the ball only as far as Devlin, who controlled it and fired through a crowded penalty area to make it 2-1.

With Swansea pressing for another equaliser, Schmid launched a long clearance forward that was chased down by Waddingham. The substitute showed great determination to hold off his marker and slot past Vigouroux to complete the 3-1 scoreline in the 98th minute.

James Bree emerged as the match-winner for the Saints, netting a neat first-half finish that ultimately proved decisive. The triumph ended a lengthy wait for supporters, marking Southampton's first league victory against their fierce local rivals since a 2-1 Premier League win back on November 13, 2004.

The fixture carried immense historical significance as only the 35th league meeting in history between these two proud clubs. Both sides approached the clash at St Mary's Stadium with high ambitions, knowing the immense value a derby success brings to the passionate fanbases involved.

Portsmouth actually began the contest looking the more industrious team as the traditional rivalry commenced under grey skies. However, it was Southampton who gradually settled into their rhythm and eventually broke the deadlock through a moment of genuine quality.

The opening goal arrived when Finn Azaz delivered a magnificent pass into the path of James Bree. The defender had cleverly slipped away from the grasp of marker Jayden Meghoma, finding himself with time and space inside the penalty area.

Bree executed a sharp first touch to control the flight of the ball before using his second touch to guide it expertly beyond the reach of goalkeeper Nico Schmid. The goal sparked wild celebrations, with the scorer racing away to celebrate directly in front of the travelling Pompey supporters.

Aside from the breakthrough moment, few clear-cut scoring opportunities of note followed before the half-time interval as both midfields engaged in a tactical battle. Neither side managed to assert complete dominance over the tempo of the game during the remainder of the opening period.

However, the hosts suffered a dramatic turning point moments before the half-time whistle sounded. Boyhood Southampton fan Cameron Bragg, already cautioned earlier in the half, picked up a second yellow card for a needless pull on Ebou Adams.

The referee had no hesitation in producing a red card, forcing Bragg to trudge off the pitch and leaving his teammates to navigate the entire second half with only ten men. The dismissal drastically altered the complexion of the contest right on the stroke of the interval.

Recognising the numerical advantage, Portsmouth head coach John Mousinho made a tactical switch at the break, introducing Adrian Segecic to help spark an equaliser. Further alterations followed just after the hour mark as the visitors attempted to press home their man advantage.

Despite dominating territory and putting sustained pressure on the Southampton rearguard, the visitors struggled to unlock a resolute defensive block. The Pompey attack increasingly lacked the necessary urgency and precision to break down the stubborn hosts.

The attacking struggles of the visiting side were starkly illustrated by the second-half statistics. Portsmouth accumulated 10 shots after the restart, yet failed to register a single effort on target, recording a paltry 0.51 expected goals metric.

The narrow victory also brought an end to a frustrating sequence of four consecutive draws in this historic fixture. It capped off an exceptionally positive week for Southampton, which had earlier received news that Tonda Eckert was given only a six-week suspended ban by the FA regarding the Spygate saga.

Southampton head coach Tonda Eckert expressed immense pride in his players when speaking after the final whistle. He remarked that the result meant everything to the club and praised the squad for showing incredible resilience.

Addressing the red card incident, Eckert admitted that it forced a complete rethink of their tactical approach. He stated that Bragg had inadvertently given them a unique challenge that would ultimately serve as a valuable learning curve for the young midfielder.

Portsmouth manager John Mousinho cut a devastated figure in his post-match assessment with broadcasters. He lamented his side's inability to capitalise on their second-half dominance and create meaningful goals from their numerous territorial advantages.

Mousinho noted that while heavy defeats are sometimes easier to accept, failing to punish a ten-man opponent after creating so many opportunities was deeply frustrating. He acknowledged that his team simply must be much more clinical in future outings.

The historic fixture remains one of English football's most fiercely contested regional pairings, steeped in tradition and fierce animosity. Matches between Southampton and Portsmouth routinely capture the imagination of the wider footballing public due to their intense atmosphere.

As the Championship season progresses, this hard-earned derby triumph could provide a massive psychological boost for Southampton's campaign. The ability to grind out a result under severe adversity highlights the character cultivated within the squad by the coaching staff.

Conversely, Portsmouth will be left to rue missed opportunities as they review the statistics from a fixture they ultimately let slip through their fingers. Both clubs will now turn their attention back to the grueling demands of the wider league fixture list.