So Saints look on course for another top-10 finish, while Boro suffer a rather meek exit from the Premier League, albeit with an industrious final flourish in front of their home fans.
But it's the hope that kills you and Boro run out of time to find an equaliser on their final match at the Riverside before dropping back to the Championship.
Jay Rodriguez nearly has his second and Saints' third but his effort slides just wide.
Neat footwork from Steven Davis in the build-up but Boro still have a sliver of hope.
So close to an equaliser for Boro and it's Calum Chambers against his former club.
The defender cracks an effort on target and forces Fraser Forster into a fine save.
And that's Long's afternoon over as he's replaced by Charlie Austin.
Heartening scenes for Saints fans as the striker returns from his long-standing shoulder injury.Copyright: Reuters
Boro captain Ben Gibson picks up a booking for a lunge on Shane Long.
Saints have been guilty of easing off since that Shane Long penalty miss and now find themselves in a nervy spell to end the game.
That said, Boro have not looked like creating much from open play. The visitors will have to keep concentrating from set pieces though.
Middlesbrough get another corner but can't score from this one as Southampton switch on and clear.
Moving towards the last 10 minutes at the Riverside - any late drama on the cards?
Steven Davis is on for Pierre-Emile Hojbjerg.
Boro have been dreadful but have a lifeline as Viktor Fischer's corner is headed in by Patrick Bamford.
It's not so much a header as the striker being in the right place at the right time for the ball to strike him and fall in.
Still, it's his first goal since rejoining Boro in January. Indeed, it's his first goal since April 2015.Copyright: Reuters
Corner for Middlesbrough, is there a way back into this game?
Marten de Roon tries to repeat that famous Thierry Henry goal against Manchester United, controlling a flick-up and turning and firing but his effort goes over.
Boro not learning their lesson as Nathan Redmond is in a ridiculous amount of space on the left again, this time seeing his effort slide narrowly over the bar.
A dreadful piece of keeping from Guzan was matched by a dreadful penalty from Long there.
The striker had the pace to get to the through-ball ahead of Guzan, who suffered the indignity of his own fans begging Anthony Taylor to send the America off.
Long will be disappointed in his effort, but truthfully it should not matter much to the outcome of this game.
Dearie me, Shane Long has belted his penalty up and over, via a touch off the top of the crossbar.Copyright: Reuters
Bad to worse for Boro as Shane Long is felled by Brad Guzan in the area and Anthony Taylor points to the spot.
Alvaro Negredo, in a bit of a huff, clatters through the back of Maya Yoshida.
The Spaniard is lucky to avoid a booking.Copyright: Reuters
Boro boss Steve Agnew has seen enough as he makes a double change.
Adam Forshaw and Stewart Downing are off in favour of Viktor Fischer and Grant Leadbitter.
It's over. And it's over in terrible style for Middlesbrough thanks to Nathan Redmond's delicious finish.
The half-time replacement is in quite a staggering amount of space on the left edge of the area as he is picked out, before cutting inside one folorn attempted tackle and curling a brilliant strike into the top corner.
Brad Guzan had no chance but it was woeful defending from Boro.Copyright: Reuters