ALEXIS Sanchez produced a moment of brilliance on his 100th English Premier League appearance as Arsenal saw off Southampton 2-0 to maintain their late top-four push.
The Chilean had toiled with his teammates at St Mary's but he elevated a low-key Gunners display just before the hour mark, his quick feet and cool finish breaking the deadlock before substitute Olivier Giroud (82) sealed a win to keep Champions League qualification in sight.
Defeat was tough on a Saints side that had crafted the better openings and forced Petr Cech into fine first-half saves from Manolo Gabbiadini and Nathan Redmond.
Injury before the break to Alex Oxlade-Chamberlain was a sour note but Arsene Wenger's men, given renewed hope by victory against Manchester United at the weekend, ended a 14-year barren league run on the south coast at the most crucial of times to climb to fifth in the table.
They still require their rivals to slip up if they are to qualify for the Champions League for a 20th successive season but have now closed in to within three points of Manchester City and four of Liverpool, with a game in hand on the Reds.
Southampton had not mustered a shot on target during Sunday's goalless draw with Liverpool but here they threatened from kick-off, Nathan Redmond dangerous first with a cross and then a cut-back, which Steven Davis ballooned behind.
Arsenal - with Shkodran Mustafi in for Laurent Koscielny - eased into the contest, waiting patiently for a break, but though Oxlade-Chamberlain gave his marker the slip with a drop of the shoulder, Aaron Ramsey's first-time swipe at the square ball flew wide.
A Cech save at Dusan Tadic's feet was a warning of Southampton's threat on the counter and despite Arsenal's growing authority, the hosts might have gone ahead on the half hour, Gabbiadini denied as Cech spread himself superbly to block.
Jack Stephens timed a tackle perfectly in the other box to thwart Mesut Ozil, the contest suddenly sparking, but Wenger suffered a setback shortly before the interval when Oxlade-Chamberlain limped off, Hector Bellerin sent on in his place.
Redmond struck from range, forcing Cech to claw away (41), and Saints picked up where they left off at the restart, even if Davis miscued again when Gabbiadini rolled into his path.
Sanchez, struggling to make an impact, grimaced as he was pulled up for a foul throw and Wenger looked on nervously as his side struggled for inspiration.
But the breakthrough came in style in the 59th minute, Arsenal's talisman pivoting as he collected an Ozil ball to feet then cutting back inside to fox two defenders before slotting low for his 20th goal of the season.
A Xhaka long-ranger made Forster work as Arsenal finally upped the tempo, though James Ward-Prowse might have done better with a decent Ryan Bertrand delivery.
Sofiane Boufal took his cue from Sanchez as he twisted between yellow shirts, only to fire well over the bar, but Giroud - sent on with 10 minutes left - made a swift impact to settle nerves, heading Ramsey's nodded assist beyond Forster to keep hopes of a familiar season finish alive.
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