Kyle Vassell hoofed beyond the despairing lunge of Alex Gogic to net the only goal of the game
Kilmarnock sealed fourth place in the Scottish Premiership and safe passage to the Europa League second qualifying round with a dogged victory over St Mirren.
Kyle Vassell walloped in the only goal after a devastating counter eight minutes before the interval.
Marley Watkins and Robbie Deas spurned opportunities to double the away lead, while, in a fiercely contested tussle, St Mirren struggled to convert possession into clear-cut openings.
The hosts can no longer catch Kilmarnock, but are within touching distance of Europa Conference League qualification, sitting five points clear of sixth-placed Dundee with two matches remaining.
The decisive moment was a bolt from the blue in a first half of little goalmouth action.
Danny Armstrong seized on an errant St Mirren pass and prodded Marley Watkins into space down the right.
The attacker surged into the box and squared for his captain, whose cute first touch bamboozled the desperate pursuers, before his second battered the ball home.
Watkins had chances in either half, the best of them when Alex Gogic inexplicably clipped into his opponent’s path, but he was denied by Zach Hemming.
The St Mirren goalkeeper soon delivered another big save from Robbie Deas’ looping header.
Toyosi Olusanya was St Mirren’s chief attacking menace with his speed and running power.
His two first-time efforts were as close as the home team came; one whizzing wide from a Ryan Strain cross, the other, from distance, rattling the crossbar after a terrific ball from Conor McMenamin.
Player of the match - Marley Watkins (Kilmarnock)
The Wales international was a constant thorn in St Mirren's side, providing a classy assist for Vassell and twice bringing Zach Hemming into impressive action.
McInnes masterclass in Paisley - analysis
This was the kind of match, and performance, upon which Derek McInnes has constructed his formidable reputation.
Kilmarnock are brilliantly coached and organised, evident in their defensive structure once Vassell had punched them ahead.
They created a greater quantity – and quality – of chances with a far more modest share of possession, with Watkins in particular threatening to widen the gap.
Kilmarnock spent most of the second half compact and combative, and largely absorbed whatever was tossed at them with minimal fuss. Vintage McInnes.
And just rewards for the manager and his team, who have surged from the Championship to the Europa League in two years.
St Mirren’s home record is excellent, losing only to the four teams above them in the table, but their failure to transfer swathes of ball and territory into a killer play was their undoing.
Olusanya stretched the game impressively. A few accurate set-piece deliveries had Kilmarnock scrambling second balls away. But Stephen Robinson’s troops could not carve out a glaring opportunity for Mikael Mandron.
What they said
St Mirren manager Stephen Robinson: "We’ve were beaten by a very good, experienced side. We lack a little bit of experience. And it's a mistake for their goal.
"We have not played at our maximum. Kilmarnock can grind it out and that’s something we have to learn from. We had a right go and just couldn’t find a goal."
Kilmarnock manager Derek McInnes: "It was important we had another big hurrah in us and we were good enough in difficult circumstances.
"It’s quite fitting my captain scores the goal that gets us to Europe. As a front two, Kyle and Marley Watkins have been terrific."
What's next?
St Mirren host Hearts on Wednesday(19:45 BST), while Kilmarnock welcome title-chasing Celtic (19:30 BST).
