The Saints, who could easily have been ahead had it not been for two stunning blocks from Boro debutant Adilson Malanda, had no answer to the home side’s attacking rejuvenation in a 12-minute spell after the restart.

Despite a hint of offside that was waved away, Morgan Whittaker slotted the opening goal below Gavin Bazunu following Matt Targett’s through pass nine minutes into the second half.

Sam Silvera’s fine touch and finish extended the lead before Whittaker converted Aidan Morris’ low delivery into the box and Alan Browne tapped in the fourth after Bazunu had denied the lively Hayden Hackney.

Hellberg was delighted with the performance of French defender Malanda, whose two goal-saving blocks either side of half-time paved the way for a vital win after he received international clearance before the game for his move from Charlotte FC.

“That was such a good performance,” Hellberg said of Malanda. “To have a centre-back, and playing in the right spaces, with that height, is needed.

“I see myself as an offensive coach, but I love the defensive side of things. Even when the goals haven’t come, you couldn’t see the bad body language anywhere in the players. They have been unbelievable.

“This win is about the players, characters, how I see them work at training ground, how they have lifted each other, stayed positive, it has been unreal to play well and not get the points we deserved.

“The business of results is to win games. We saw a group of players today who have kept playing and been brave, and the second half was an unbelievable performance.”

The victory, which ended a run of four matches without a win and without scoring a goal, lifted Middlesbrough back into the top two and closed the gap on leaders Coventry to six points.

Southampton boss Tonda Eckert was left frustrated that the first goal was allowed to stand. The bigger picture, though, is that Southampton have gone six matches without a win.

Eckert said: “We saw two games in the end. We played one game in 55 minutes and the other game after that. The first 55 minutes we played a decent game, had more than enough chances, but the second half was not good enough.

“It was a big disappointment. It is not about pointing fingers, the disappointment is huge but there’s no divide. We can talk about the game after 55 minutes, it was nowhere near good enough.

“The first goal changed everything, changed confidence. From what I have heard it was a clear offside decision. It was a tough call and when you invest so much into the game, the second half of the game was not good enough. We needed to score the first goal.

“I expect all the players to go over to the fans (at the end of the game), we are grateful to the support. We need to represent this club in a better way.”