London - Arsenal's push to win the Premier League title for the first time in 12 years suffered a setback as Southampton goalkeeper Fraser Forster produced a magnificent display in Tuesday's 0-0 draw at the Emirates Stadium.
Arsene Wenger's side dropped to fourth place following their fourth successive league game without a win and they now lie five points behind leaders Leicester.
It was a frustrating evening for Wenger as Forster made a string of fine stops that enabled Saints manager Ronald Koeman to continue his excellent sequence of results against the Gunners boss.
Forster only recently returned to first-team action for Southampton after a 10-month layoff with a horror knee injury sustained against Burnley last March.
The 27-year-old has kept four clean sheets in his four matches and this was the best yet.
For Koeman, the stalemate showed once again that he has worked out how to frustrate Wenger with his tactics.
In five matches against Arsenal since taking over at Saints, Koeman has enjoyed three victories, savoured three clean-sheets, and experienced just the one defeat.
Though Arsenal struggled to find any fluency or rhythm in the opening exchanges, evidence of their ability to stretch a defence in an instant came in the 12th minute.
Alexis Sanchez, making his first Premier League for two months after returning from a hamstring injury, pinpointed the run of Mesut Ozil from the halfway line.
The pass over the Southampton defence was deftly controlled on Ozil's left foot, stopping it dead in midair, but the eventual shot lacked the power to trouble Forster.
Forster was to deny Ozil again eight minutes later with an example of sheer strength and athleticism.
Olivier Giroud headed down a cross from the right by Hector Bellerin and Ozil skipped in front of the defence, beating the offside trap, to knock it goalbound.
Yet the strong left hand of Forster managed to divert the ball away for a corner.
In the second half, it remained the Forster Show as he made several stops and blocks to thwart the Gunners' attack.
His right hand pushed a curling effort from Giroud over the crossbar on 47 minutes.
Shortly afterwards, he impressively saved twice from Theo Walcott; the first time with his feet, then with his palms when the Arsenal substitute seemed odds-on to score.
Later on, he scrambled across his goal to push wide a Sanchez effort for a corner.
Should he continue like this for the rest of the season, it is fair to say that Forster will push Joe Hart hard for an England starting position come the Euro 2016 finals and Saints fans serenaded him with chants of "England's No.1".
However, from an attacking perspective, Southampton offered little to grab a memorable win.
Sadio Mane lacked the cutting edge to trouble Arsenal goalkeeper Petr Cech.
Disappointingly for Koeman, he was denied the chances to hand a first start to new striker Charlie Austin.
The recent signing from QPR picked up a slight knock in the build-up and a decision was taken not to risk his long-term fitness.
In Austin's absence, Shane Long carried much of the scoring responsibility.
But unlike the 4-0 victory over Arsenal at St Mary's on Boxing Day, when Long scored twice and terrorised defender Per Mertesacker, the Irish international was a fairly anonymous figure this time.