Imagine Adnan Januzaj's second goal at the Stadium of Light on Saturday evening and you are some way to visualising the finish of Richard Smallwood as he volleyed Boro into the lead with just short of six minutes played.
Picked out by Emmanuel Ledesma well to the left of centre inside the penalty area, the Dormanstown-born midfielder unleashed an unstoppable shot across Cody Cropper.
The Saints looked to hit back quickly and won a succession of corners but Dimi Konstantopoulos was a match for efforts from Jake Flannigan and Omar Rowe.
Midway through the first half Boro almost made it two when a fine Cameron Park cross on the right was powerfully headed by Bryn Morris but Cropper produced a smart save with his legs.
The value of the save became even greater as the visitors swept upfield to equalise.
With 23 minutes played Omar Rowe took the initiative to the left edge of the penalty area and cut inside. With better-placed team-mates to his left he elected to keep possession. Making such decisions you have to be good and he was as he produced a shot of some quality which flew on the angle past Konstantopoulos.
By now the U21 version of the Premier League side currently flying high were creating the greater number of chances, settling after a slow start to see a lot more of the ball.
Konstantopoulos tipped over as midfielder Harrison Reed went for goal from 20 yards and again when Rowe threatened then shot once more.
A right-wing corner from Rowe ought to have led to a second Southampton goal but Jake Sinclair headed wide from close range at the back post.
Entering injury-time at the end of the first half Cropper was called into action as Park shot low to the near post. A smart effort and smart stop was the last action of a lively first half.
Half-time: Boro U21 1 Saints U21s 1
The entertainment showed no signs of relenting as Boro set about their task in good style from the start of the second half.
It took just four minutes of the half to edge into the lead with a smartly worked rounded off by Ledesma, who set up Luke Williams
Another really smart move brought another goal on 56 minutes when Emmanuel Ledesma played a one-two with the impressive Smallwood and cracked home in style.
The Argentinian should have added a fourth when brought down inside the penalty area less than a minute later but his spot kick was well saved by Cropper diving away to his left.
Boro were moving sweetly now and Williams saw a low shot well saved when sent in behind the back line.
Williams turned provider on 82 minutes when setting up sub Bradley Fewster - on for Ledesma who had limped off a few minutes after a painful looking injury when his Achilles was accidentally stepped on. Fester's effort was a good one but so too was the save from Cropper.
Southampton, second best in the second half, were spirited and Lloyd Isgrove danced his way into the penalty box on the right but his low cross was met by a thumping clearance.
There was a lot to admire about Boro's performance and they were good value for their win.
Scorers: Smallwood,6; Rowe, 23; Williams, 48; Ledesma, 56.
Boro: Konstantopoulos; Bennett, Hines, Jackson (Capt), Meling, Morris, Jones, Smallwood, L Williams, Ledesma (Fewster 67), Park. Unused subs: Fryer (gk); Weledji, B Halliday, Sirrell.
Southampton: Cropper; McCarthy, Colmer (Young 86), Reed, Stephens (Capt), Turnbull, Isgrove, Flannigan (Gape 49), Lee, Sinclair (Seager 60), Rowe. Unused subs: Britt, Branker.
Boro: Hines, 17, foul; Jackson, 79, foul.
Southampton: McCarthy, 77, handball; Rowe, foul, 85