Arsenal manager Mikel Arteta admitted his side's form was "a real worry" after Southampton won at St Mary's to inflict a third successive defeat on the top-four chasing Gunners.
Jan Bednarek scored the game's only goal late in the first half after the visitors had failed to adequately deal with a Saints corner.
Bukayo Saka was denied from point-blank range by Southampton goalkeeper Fraser Forster with the score still goalless, but further clear-cut openings proved hard to come by for Arsenal until the closing stages of the second half.
Emile Smith Rowe forced another fine save out of Forster after latching on to Yan Valery's attempted clearance, before Martin Odegaard dragged a left-footed shot wide of the near post after cutting in from the right.
Forster produced yet another impressive stop to deny Granit Xhaka late on as Arsenal desperately piled forward in search of an equaliser.
"We've lost games in different ways - to lose the way we did today is difficult to explain," Arteta told BBC Match of the Day. "If you saw the game, you'd say Arsenal had won comfortably.
"You have to put the ball in the net. You have to make the decisive moments count to win football matches and at the moment we're not doing that."
The Gunners remain three points behind fourth-placed Tottenham - who were beaten at home by Brighton earlier on Saturday - although they do still have a game in hand on their north London rivals.
Southampton, meanwhile, climb to 12th after claiming their first league win since February.
Reaction to Southampton v Arsenal and the rest of Saturday's Premier League action
Go straight to all the best Arsenal content
Visit our Southampton page
Magnificent Forster keeps Gunners at bay
Southampton 1-0 Arsenal: Mikel Arteta disappointed with 'painful' Saints defeat
Following lacklustre displays at Crystal Palace and at home to Brighton last weekend, Gunners fans may have hoped this trip to St Mary's would prove to be an ideal fixture to reignite their top-four push.
Saints had lost five of their past six games in all competitions before Saturday and conceded 19 goals in the process - including a 6-0 capitulation at home to Chelsea in their last match. They had also won only one of their past 12 meetings with Arsenal in the Premier League.
The hosts had Forster to thank for keeping the score goalless in the early stages of the first half, the veteran goalkeeper getting down low to palm Gabriel Martinelli's curling shot past the post before brilliantly tipping Saka's close-range effort over the bar following an error from Valery.
Although the Gunners continued to dominate possession as the half wore on, they lacked the tempo to create further openings against a resolute and defensively organised Southampton, who punished Arsenal when Bednarek fired home his fourth goal of the season with a minute of the first half remaining.
When Arsenal did manage to penetrate the Saints rearguard late in the second half, they found Forster in inspired form. The 34-year-old did magnificently to parry Smith Rowe's goal-bound effort wide before getting in the way of a low Saka shot.
Forster also managed to get his fingertips to Xhaka's curling strike with the clock ticking towards 90 minutes - although the Switzerland international's effort may have been heading narrowly wide.
Southampton 1-0 Arsenal: Ralph Hasenhuttl pleased with 'important' three points for Saints
"It wasn't so sure he could play today," Saints manager Ralph Hasenhuttl told BBC Match of the Day when asked about Forster's display. "He had a problem with his ankle, but we needed a goalkeeper like him in such a game today.
"The most important thing is the clean sheet after six or seven games [without one]. We've played much better games, especially with the ball, but today the target was a different one."
Arsenal still have a game in hand on Spurs in fourth but with matches against Chelsea, Manchester United and West Ham coming up in the next fortnight, this will go down as a missed opportunity for Arteta and his players.
Benjamin White (Arsenal) is shown the yellow card for a bad foul.
Foul by Benjamin White (Arsenal).
Mohamed Elyounoussi (Southampton) wins a free kick on the left wing.
Foul by Granit Xhaka (Arsenal).
Shane Long (Southampton) wins a free kick on the right wing.
Attempt blocked. Gabriel Martinelli (Arsenal) right footed shot from the centre of the box is blocked. Assisted by Albert Sambi Lokonga.
Attempt missed. Martin Ødegaard (Arsenal) left footed shot from outside the box is close, but misses the top left corner following a corner.
Corner, Arsenal. Conceded by Fraser Forster.
Attempt saved. Granit Xhaka (Arsenal) left footed shot from outside the box is saved in the bottom right corner. Assisted by Emile Smith Rowe.
Attempt blocked. Granit Xhaka (Arsenal) left footed shot from outside the box is blocked. Assisted by Albert Sambi Lokonga.
Albert Sambi Lokonga (Arsenal) wins a free kick in the defensive half.
Page 1 of 5src="https://rewind
Navigate to the next pagesrc="https://next
Navigate to the last pagesrc="https://forward
Our coverage of your Premier League club is bigger and better than ever before - here's everything you need to know to make sure you never miss a moment
Join the conversation
These comments are now closed.
Comment posted by WHO DARES WINS, at 17:00 16 AprWHO DARES WINS
17:00 16 AprUTD,SPURS & ARSENAL are fighting it out not to finish in the TOP 4...
Reply posted by Beloved light panacea for twisted dark, at 17:02 16 AprBeloved light panacea for twisted dark
17:02 16 Aprto WHO DARES WINSBeloved light panacea for twisted dark replied: Spurs 12 points from last 15
Comment posted by Cosmic Hobo, at 16:58 16 AprCosmic Hobo
16:58 16 AprI almost feel ashamed to be a Gooner. There's almost a sense of inevitability that they'll always blow it. Well done Saints nevertheless.
Reply posted by What barn door, at 17:01 16 AprWhat barn door
17:01 16 Aprto Cosmic HoboWhat barn door replied: Funny how your fans were making fun of Spurs after their game. Not really pulling up any trees yourself.
Comment posted by RDW_SW, at 16:58 16 AprRDW_SW
16:58 16 AprBottle job trophy taken back then. A team that cant score against let alone beat Palace, Brighton and Southampton when it matters most probably doesn't deserve top 4. Just not good enough.
Reply posted by pab0967, at 17:18 16 Aprpab0967
17:18 16 Aprto RDW_SWpab0967 replied: Neither North London club are
Comment posted by 69-4T, at 17:20 16 Apr69-4T
17:20 16 AprLet's give Southampton some credit here on this platform. Arsenal are not good enough to handle pressure in games that they should have won. How would Arsenal cope in Europe if they qualify (that's if they qualify at all). Congrats Southampton 👏
Reply posted by Ybli, at 17:23 16 AprYbli
17:23 16 Aprto 69-4TYbli replied: As an Arsenal fan, I completely agree.
Comment posted by iufgn, at 16:59 16 Apriufgn
16:59 16 Aproh dear, three matches that ought to have been three wins and a total of 0 points from them. Not sure this team is ready for European football. Need to buy another 5 or 6 players n the close season as the squad isn't good enough
Reply posted by dan, at 17:03 16 Aprdan
17:03 16 Aprto iufgndan replied: Is that Spurs or Arsenal
Comment posted by 1963tiger, at 16:58 16 Apr1963tiger
16:58 16 AprArsenal trying to fnish the season the way they started it?
Reply posted by Ad, at 17:01 16 AprAd
17:01 16 Aprto 1963tigerAd replied: Arsenil are the new Spurs...!!!! Hahahahahaha
Comment posted by Cole, at 17:02 16 AprCole
17:02 16 AprSometimes Hassenhutl seems out of this depth completely, and then other times he pulls off results like these! Erratic, but still big respect to him and to Southampton for having some sticking power after a bad run.
Reply posted by Vincent, at 17:17 16 AprVincent
17:17 16 Aprto ColeVincent replied: Take the resources of the two teams into account, he's better than Arteta. Resources to win ratio, Arteta's mid-table at best, maybe even Lampard level.
Comment posted by coolspex, at 17:00 16 Aprcoolspex
17:00 16 AprArsenal more spursy than Spurs today, thanks saints COYS
Reply posted by Al_Bundy, at 17:08 16 AprAl_Bundy
17:08 16 Aprto coolspexAl_Bundy replied: The word should be changed to arsey.
Comment posted by Smudger, at 17:13 16 AprSmudger
17:13 16 AprAmazing performance by Forster, great result. COYS.
Reply posted by sam, at 21:43 16 Aprsam
21:43 16 Aprto Smudgersam replied: I've always liked Forster think he's a great keeper. I feel sorry for him, because as soon as Mccarthy back fit he'll be dropped again.
Comment posted by Huggie, at 17:00 16 AprHuggie
17:00 16 AprThe battle for who doesn't want top 4 is really hotting up
Comment posted by Warm beer, at 16:57 16 AprWarm beer
16:57 16 AprYou goonies never learn do you, all over the Spurs HYS a couple of hours ago, should have waited a bit.
Reply posted by RDW_SW, at 16:59 16 AprRDW_SW
16:59 16 Aprto Warm beerRDW_SW replied: as if you lot don't do the same
Comment posted by Tackle22, at 16:59 16 AprTackle22
16:59 16 AprSpurs "outspursyed" by Arsenal! Love it!
Reply posted by margaret, at 19:35 16 Aprmargaret
19:35 16 Aprto Tackle22margaret replied: New in investment coming in from 🇨🇳 China, who is laughing now ?
Comment posted by LionelRhodes, at 17:03 16 AprLionelRhodes
17:03 16 AprOK Arsenal played much better then last two games...but still can't score a goal to save our lives at the moment! It's simple really - we don't have any good strikers. Lacazette and Eddie are simply not good enough - and we don't deserve Champs League. Arsenal need to go & buy two good strikers, LB cover for KT, a world class midfielder - or two. Our squad cannot cope with an injured Partey & KT.
Reply posted by AK, at 17:45 16 AprAK
17:45 16 Aprto LionelRhodesAK replied: We all know the problems. Getting the best to come is so difficult. With vlahovic In the team the top4 would’ve been a shoe-in. Brave from Arteta not to panic buy any old crap but without top4 don’t expect much improvement soon.
Comment posted by charlie, at 19:53 16 Aprcharlie
19:53 16 AprWhy does the media always belittle everyone outside the top 6, the mighty Southampton beat Arsenal and its Arsenal having a bad day not a peep bout Saints stunning performance after last weeks f***k up against chelsea
Reply posted by barrykins, at 21:10 16 Aprbarrykins
Reply posted by Fan Of Whoever Plays Man Utd, at 21:55 16 AprFan Of Whoever Plays Man Utd
21:55 16 Aprto Stuart Fan Of Whoever Plays Man Utd replied: All just trying to do their best to help Man Utd to finish 4th, as it is obvious that Utd can do it on their own merits.
Comment posted by Pablo, at 16:57 16 AprPablo
16:57 16 AprAbysmal from Arsenal
Reply posted by The Spin Doctor, at 17:02 16 AprThe Spin Doctor
17:02 16 Aprto PabloThe Spin Doctor replied: Man Utd would like to thank Arsenal for keeping them in the 4th place race. Much appreciated!
Comment posted by Owain, at 16:57 16 AprOwain
16:57 16 AprArsenaly.
Reply posted by Ad, at 17:01 16 AprAd
17:01 16 Aprto OwainAd replied: Arsenil....!!!
Comment posted by Jaimo, at 16:58 16 AprJaimo
16:58 16 AprThis eases the blow of Spurs blowing it… Nice one Saints.
Reply posted by Ben Kensolpalpawalkerbi, at 17:15 16 AprBen Kensolpalpawalkerbi
17:15 16 Aprto JaimoBen Kensolpalpawalkerbi replied: I'm almost hoping that United blow fourth place this season, if only so the new manager gets carte blanche to boot half of the United team out the door, rather than us stumbling over the line (as all three sides are) and the owners thinking we've 'had a fairly successful season'.
Nobody seems to particularly want this final CL spot...
Comment posted by spurs1882, at 16:58 16 Aprspurs1882
16:58 16 AprI knew arsenal wouldn’t win this game because they just can’t score at the moment.. just so disappointed we lost today! But seriously don’t anyone want this 4th place!
Reply posted by COYS 1, at 17:00 16 AprCOYS 1
17:00 16 Aprto spurs1882COYS 1 replied: Thank you Saints. Our loss doesn’t feel so bad now.
Comment posted by wemarchon, at 17:19 16 Aprwemarchon
17:19 16 AprBeautiful result Saints. Thank you for listening.