Match ends, Motherwell 5, St. Mirren 0.
Motherwell dismantled a vulnerable St Mirren with ease to go 10 points clear of the Paisley side who are rooted to bottom of the Scottish Premiership.
Lee Erwin's near-identical left-footed double put them on course for their third consecutive win.
Scott McDonald steered in another before half-time and John Sutton added two more from close range.
It leaves St Mirren perilously close to surrendering their Premiership place and Well's survival hopes enhanced.
This was also the North Lanarkshire club's biggest win since a 6-0 victory over Morton in the Scottish Cup in 2012.
The Fir Park side are still three points behind 10th-place Ross County, who won 1-0 at home to St Johnstone.
Six games remain for Gary Teale's St Mirren to somehow extract themselves from the foot of the table, and that starts with another proverbial 'six-pointer', maybe even a 'nine-pointer', versus Ross County on Monday.
What an impact 21-year-old Erwin is having on Motherwell's increasing chances of avoiding the relegation play-off spot, the striker scoring his third goal in two games against their hapless visitors.
His burgeoning reputation has already drawn talk of a "massive future" from experienced team-mate Stephen Pearson, and much of Erwin's joy comes from using his frame to great effect.
Both his goals were assisted by the ever-lively Lionel Ainsworth, who has re-captured the form of last season in recent games after a quiet opening six months of the campaign.
For the first, Erwin received Ainsworth's low cross with his back to goal and six-yards out, but wasted no time in spinning his defender and shooting low into the near corner.
St Mirren's Kieran Sadler dragged wide of George Long's goalmouth before Marvin Johnson's volley and Stephen McManus's diving header were closer to extending Motherwell's lead.
Erwin succeeded where they failed. The former Arbroath loanee pulled off the same trick; gathering Ainsworth's cross-come-shot with back to goal and swivelling to curl low into Mark Ridgers' far corner.
The killer third was inflicted by McDonald moments before the break. Former Kidderminster Harriers winger Johnson collected Ainsworth's stabbed cross and calmly cut the ball back for the Australian to side-foot calmly home from eight yards. Game over.
Stephen Thompson was introduced for the second-half and Saints centre-back Marc McAusland gave Long a rare piece of work to do saving a goal-bound header.
But it was the head of Sutton that helped Motherwell's goal difference further, escaping the attentions of Viktor Genev to dive and head Johnson's free-kick into the top corner.
Stevie Mallan's curler almost gave Saints a consolation but came back off the post and Sutton administered more pain soon after by scrambling in a blocked McDonald shot.
- 7AinsworthSubstituted forThomasat 75'minutes
- 48PearsonSubstituted forGrantat 64'minutes
- 19ErwinSubstituted forSuttonat 71'minutes
- 4McAuslandBooked at 51mins
- 6GoodwinSubstituted forBrownat 83'minutes
- 17DaytonSubstituted forWyldeat 45'minutes
- 10SadlierSubstituted forThompsonat 45'minutes
- 7McGinnBooked at 82mins
- Craig Thomson
- Shots on Target
Second Half ends, Motherwell 5, St. Mirren 0.
Attempt saved. John McGinn (St. Mirren) left footed shot from outside the box is saved in the top centre of the goal.
Attempt missed. Marvin Johnson (Motherwell) right footed shot from the centre of the box is just a bit too high.
Corner, St. Mirren. Conceded by Louis Laing.
Substitution, St. Mirren. Adam Brown replaces Jim Goodwin.
Foul by Conor Grant (Motherwell).
Jim Goodwin (St. Mirren) wins a free kick in the defensive half.
Attempt blocked. Jim Goodwin (St. Mirren) right footed shot from outside the box is blocked.
John McGinn (St. Mirren) is shown the yellow card.
Anthony Straker (Motherwell) wins a free kick in the defensive half.
Foul by John McGinn (St. Mirren).
Goal! Motherwell 5, St. Mirren 0. John Sutton (Motherwell) left footed shot from very close range to the bottom left corner.
Attempt missed. Scott McDonald (Motherwell) right footed shot from outside the box is close, but misses to the right.
Stephen Mallan (St. Mirren) hits the left post with a left footed shot from the centre of the box.
Attempt missed. John Sutton (Motherwell) header from the centre of the box is just a bit too high.
Corner, Motherwell. Conceded by Sean Kelly.
John Sutton (Motherwell) wins a free kick in the attacking half.
Foul by Marc McAusland (St. Mirren).
Substitution, Motherwell. Dom Thomas replaces Lionel Ainsworth.