Match ends, Ross County 1, St. Mirren 3.
John Hughes says the "penny has to drop" for his Ross County side after they slipped into the Scottish Premiership relegation play-off place after defeat by St Mirren.
Jordan White's cute flick had County set to go six points clear of bottom club Hamilton Academical.
However, Lee Erwin's fine header early in the second half levelled the score.
Then Ilkay Durmus gave the away side the lead before Jamie McGrath made sure of the win with a late penalty.
"We won't win any games if we're conceding two or three goals," Hughes said. "There must be something wrong and we have to sit down and look at it.
"We're looking for the answers and solutions and hopefully we can come up with them."
The defeat means County sit three points above Hamilton and slip two behind Kilmarnock, while St Mirren climb into seventh place.
The home side would have been keen to take advantage of Hamilton's defeat by Motherwell, but it was St Mirren who started more brightly and almost took the lead inside the first minute.
Jay Henderson, a 19-year-old making his first start, nearly converted a Cammy MacPherson cross with Leo Hjelde putting his body in between.
The away side continued to have the majority of play but were unable to make the most of that dominance and County took advantage. A quick free-kick found Billy Mckay, whose ball into the area was eventually cleared before being returned by Jason Naismith towards White, who shrewdly nudged past Jak Alnwick.
The goalkeeper was involved again as he stretched spectacularly to keep out Jordan Tillson's looping shot just before the interval.
The break was a welcome one for Jim Goodwin's side as they came out the blocks much improved and quickly equalised through Erwin.
Alnwick's long ball found Richard Tait, who chested past his man and delivered a perfect cross into the path of Erwin to bullet a header past Ross Laidlaw.
Hughes wasn't content with a point and opted to make a triple change on the hour, but it was the away side who continued to threaten before taking the lead through Durmus.
The Turkish winger finished off a sweeping counter attack after Collin Quaner latched onto Erwin's long ball forward then cut back to find the onrushing Durmus, who finished neatly.
County could not regain a foothold in the game as the visitors began to create further opportunities.
Kyle McAllister cracked the post following a Quaner flick on and MacPherson saw two efforts drift just wide of the post in the final stages.
McGrath ensured the points would head back to Paisley as he converted a penalty for his 14th goal of the season after Hjelde slid in to block a MacPherson shot with his arms outstretched.
Man of the match - Ilkay Durmus
What did we learn?
This was ultimately a big missed opportunity for County. Hughes' decision to go for it in the second half could come back to haunt them, but they are still in the driver's seat to avoid automatic relegation.
For St Mirren this was another flash of their ever more impressive credentials. It's three years to the day they clinched the Scottish Championship title and, since the appointment of Goodwin, they have gone from strength to strength.
Despite their injury troubles they were comfortable in the end and all focus should now turn to possible Scottish Cup glory.
What did they say?
Ross County manager John Hughes: "The goals we conceded are the same as against Inverness and Kilmarnock - it's bread and butter stuff. It's the do's and the dont's of football.
"I'll never question their commitment but it's the fundamentals we have to get right."
St Mirren manager Jim Goodwin: "At half time, it was important to encourage the players and help them believe that if they got the next goal then they could go again and win the game."
"All in all I'm really satisfied considering we're up here with a real lack of numbers, not loads of options off the bench. I think the players deserve enormous credit."
County travel to Tannadice to face Dundee United a week on Saturday (15:00 BST), while St Mirren face Kilmarnock away from home in the Scottish Cup this Monday (19:45) live on BBC Scotland.
- 23NaismithSubstituted forSpittalat 76'minutes
- 4HjeldeBooked at 90mins
- 11VigursSubstituted forHyltonat 67'minutes
- 6DraperSubstituted forShawat 82'minutes
- 7GardyneSubstituted forCharles-Cookat 67'minutes
- 9MckaySubstituted forPatonat 67'minutes
- 30HendersonSubstituted forMcAllisterat 68'minutes
- 2TaitSubstituted forFinlaysonat 90+4'minutes
- 20DennisSubstituted forQuanerat 68'minutes
- Bobby Madden
- Shots on Target
Second Half ends, Ross County 1, St. Mirren 3.
Attempt missed. Alex Iacovitti (Ross County) header from the centre of the box misses to the right. Assisted by Blair Spittal with a cross.
Substitution, St. Mirren. Daniel Finlayson replaces Richard Tait.
Goal! Ross County 1, St. Mirren 3. Jamie McGrath (St. Mirren) converts the penalty with a right footed shot to the centre of the goal.
Leo Fuhr Hjelde (Ross County) is shown the yellow card for hand ball.
Penalty conceded by Leo Fuhr Hjelde (Ross County) with a hand ball in the penalty area.
Attempt blocked. Cameron MacPherson (St. Mirren) right footed shot from the centre of the box is blocked. Assisted by Collin Quaner.
Attempt missed. Jordan White (Ross County) header from the centre of the box misses to the right. Assisted by Blair Spittal with a cross following a corner.
Corner, Ross County. Conceded by Conor McCarthy.
Attempt missed. Cameron MacPherson (St. Mirren) right footed shot from outside the box is close, but misses to the right. Assisted by Collin Quaner.
Foul by Regan Charles-Cook (Ross County).
Ilkay Durmus (St. Mirren) wins a free kick in the defensive half.
Kyle McAllister (St. Mirren) hits the left post with a left footed shot from the left side of the box.
Substitution, Ross County. Oli Shaw replaces Ross Draper.
Hand ball by Collin Quaner (St. Mirren).
Harrison Paton (Ross County) wins a free kick on the right wing.
Foul by Lee Erwin (St. Mirren).
Substitution, Ross County. Blair Spittal replaces Jason Naismith because of an injury.
Attempt missed. Cameron MacPherson (St. Mirren) right footed shot from the centre of the box is close, but misses to the right. Assisted by Kyle McAllister with a cross.