Match ends, Middlesbrough 1, Southampton 2.
Southampton remain on course for a top-half Premier League finish as they held off a late fightback from a meek, already relegated Middlesbrough.
Jay Rodriguez put Saints in front at the end of a lifeless first half, losing Calum Chambers to turn in Shane Long's cross after a neat build-up.
Half-time substitute Nathan Redmond curled an exquisite strike into the top corner on 57 minutes after being left completely unmarked by a careless Boro defence.
Boro's Brad Guzan conceded a penalty after felling Long, with sections of the home crowd calling for their keeper to be sent off by referee Anthony Taylor, only for the Saints striker to fire his spot-kick over.
Patrick Bamford scored his first goal since his previous spell at Middlesbrough in April 2015 by heading in Viktor Fischer's corner to set up a nervy finish for the visitors.
Chambers drew a fine save from Saints keeper Fraser Forster but the hosts could not find an equaliser in their final game at the Riverside before dropping back to the Championship.
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Boro sign off at home in familiar fashion
With relegation confirmed by Monday's 3-0 defeat by champions Chelsea, Middlesbrough had little to play for except professional pride and to try to end a woeful run of one Premier League victory in 19 games.
Yet that did not translate into any endeavour before the break as their all-too-familiar failings in attack were evident again. The recalled Bamford could not combine with Alvaro Negredo and Stewart Downing to regularly trouble Saints.
As bad as Boro have been at scoring goals this season, their increasing defensive frailty in the second half of the campaign is also an important a factor in their relegation. Steve Agnew's side have conceded 30 times since Christmas out of a total of 50 for the season so far.
Here they continually allowed Redmond free rein down the left flank and were duly punished soon after the break - a goal that ultimately settled the game as Boro gave themselves too much to do despite a spirited reaction in the final 20 minutes.
Under the guidance of respected chairman Steve Gibson, the club will hope to make an immediate return to the Premier League next season, having endured a seven-year absence from the top flight before this campaign.
However, captain Ben Gibson will have his suitors this summer, Negredo and Chambers will likely return to their parent clubs, while someone might take a chance on the mercurial talents of winger Adama Traore.
The future of head coach Agnew is also up in the air. Can Middlesbrough keep it together and bounce back?
Man of the match - Nathan Redmond (Southampton)
Saints revive scoring form
Southampton boss Claude Puel made seven changes to the starting line-up, handing a debut to centre-back Martin Caceres and a first start for right-back Jeremy Pied, reflecting the feeling this was a somewhat inconsequential match.
The visitors duly struggled to get going in the first half, until a simple but effective move saw Jordy Clasie stroke a ball down the right for Long to surge onto and find Rodriguez, who had cleverly checked his run for a low finish under Guzan.
That was Saints' first goal in four matches and seemed to loosen them up, especially once Redmond was introduced for Sofiane Boufal to cap a fine performance with an excellent finish.
Puel's side also ended a winless run of five games, while Charlie Austin - who remains the club's top scorer this season despite not playing since December - returned from a long-standing shoulder injury as a late substitute.
They were guilty of easing off once Guzan had conceded the penalty - Long failing to convert the chance to put the game beyond doubt and his defence compounding the error by letting Boro build momentum following Bamford's goal.
However, the task proved to be beyond the hosts and Saints look set to secure an impressive fourth-straight finish in the Premier League top 10 despite the regular departure of key players and managers.
'We haven't given the fans enough' - manager reaction
Middlesbrough boss Steve Agnew: "The supporters have been fantastic all season. They've waited a long time to get back in the Premier League and we haven't given them enough, we owed them that lap of appreciation.
"We were disappointed with the first-half performance. The penalty miss by Shane Long gave us the initiative and we took it. The goal from Patrick Bamford gave us confidence and belief but didn't get the equaliser.
On whether he would like to remain in the job next season: "Times like this are disappointing for all of us but most importantly it's about Middlesbrough getting into a position and a fantastic opportunity to bounce back."
Southampton boss Claude Puel: "It was a little difficult at the end of the game with the long ball but it was important to get a good result.
"We made seven changes and it's important for the squad - many players improve and can show they have a good spirit.
"I hope we can finish strong with the two last games at home. I'm satisfied because we have done good work with all the players."
Bamford ends long drought - match stats
- Middlesbrough have won just one of their past 20 Premier League games, losing 12.
- Bamford scored his first competitive goal since netting for Middlesbrough versus Wolves in April 2015 - 760 days ago.
- Boro have not kept a clean sheet against Southampton at the Riverside in any of their past eight league meetings, since a 3-0 win in March 1999.
- Redmond has scored seven goals in the Premier League this term, his best goalscoring season in the competition.
- Long, who has now missed two of his three penalties in the Premier League, has also gone 11 games without a goal in the competition.
Middlesbrough are away to Liverpool on the final day of the season - Sunday, 21 May, when all games kick-off at 15:00 BST.
Southampton have a rearranged match at home against Manchester United on Wednesday, with kick-off at 19:45 BST, before hosting Stoke on the last day.
- 2da Silva
- 6GibsonBooked at 86mins
- 14de RoonBooked at 90mins
- 8ClaytonBooked at 66mins
- 34ForshawSubstituted forLeadbitterat 60'minutes
- 19DowningSubstituted forFischerat 60'minutes
- 23HøjbjergSubstituted forDavisat 74'minutes
- 7LongSubstituted forAustinat 87'minutes
- 19BoufalSubstituted forRedmondat 45'minutes
- Anthony Taylor
- Shots on Target
Second Half ends, Middlesbrough 1, Southampton 2.
Ryan Bertrand (Southampton) wins a free kick in the defensive half.
Foul by Grant Leadbitter (Middlesbrough).
Attempt saved. Patrick Bamford (Middlesbrough) header from the centre of the box is saved in the centre of the goal. Assisted by Viktor Fischer with a cross.
Foul by Jordy Clasie (Southampton).
Patrick Bamford (Middlesbrough) wins a free kick on the right wing.
Attempt missed. Jay Rodriguez (Southampton) right footed shot from the centre of the box is close, but misses to the left. Assisted by Steven Davis.
Attempt saved. Calum Chambers (Middlesbrough) left footed shot from outside the box is saved in the bottom right corner. Assisted by Ben Gibson.
Hand ball by Jay Rodriguez (Southampton).
Marten de Roon (Middlesbrough) is shown the yellow card.
Jérémy Pied (Southampton) wins a free kick on the right wing.
Foul by Marten de Roon (Middlesbrough).
Corner, Middlesbrough. Conceded by Maya Yoshida.
Attempt missed. Jay Rodriguez (Southampton) header from the centre of the box is high and wide to the right. Assisted by Ryan Bertrand with a cross following a set piece situation.
Substitution, Southampton. Charlie Austin replaces Shane Long because of an injury.
Delay over. They are ready to continue.
Delay in match Shane Long (Southampton) because of an injury.
Ben Gibson (Middlesbrough) is shown the yellow card for a bad foul.
Shane Long (Southampton) wins a free kick on the right wing.