Humphrey scored the opener for Motherwell at Fir Park
A late brace of goals ensured Motherwell kept their grip of third place in the Scottish Premier League.
Chris Humphrey pounced on a slip from Patrick Cregg to lash an angled strike home after just three minutes.
St Mirren striker Gareth Wardlaw levelled on 64 minutes, blasting a shot high into the net from close range.
However, Tom Hateley converted a penalty on 87 minutes and Jamie Murphy tucked in a delivery from Alan Gow to seal the victory soon after.
It was a first home win of the campaign for Craig Brown's high-flying Motherwell, bolstering a 100% away record, while the Buddies remain bottom of the Scottish Premier League.
The Lanarkshire side got off to a great start when David van Zanten's clearing header from a Hateley free-kick found Cregg on the edge of the box, and his slip on the rain-soaked surface allowed Humphrey to crash a shot home.
The home side went for the kill, with Nick Blackman shooting just wide on 18 minutes following a Humphrey cross from the right.
Hateley was then denied an excellent Craig Samson save as the half reached its midway point. The midfielder's effort from the left edge of the box looked netbound until the St Mirren keeper stretched to turn it onto the bar and to safety.
Paul McGowan tried a hopeful shot for St Mirren from the edge of the box which home goalkeeper Darren Randolph easily smothered.
And the visitors almost equalised on 39 minutes when Hugh Murray's free-kick was flicked across goal by Michael Higdon and Wardlaw turned the ball narrowly wide.
St Mirren went close again in first-half stoppage time when, from a McGowan corner, Higdon hit the bar and then saw his follow-up cleared off the line by Stephen Craigan.
Early in the second half, Motherwell's Murphy cut inside from the left to shoot from the edge of the box, but Samson dived confidently to claim the effort.
A similar effort shortly afterwards saw Murphy send a return pass through the box for Keith Lasley, but the ball was stolen away from the midfielder's feet by John Potter.
Goalmouth chances had dried up but St Mirren found themselves level when Motherwell failed to clear their lines following McGowan's earlier free-kick, and when the same player put the ball back into the right-hand side of the box, Wardlaw lashed home.
Randolph had to turn McGowan's cross over the bar moments later as St Mirren sensed a shift in the balance of play.
However, it was to be Motherwell substitute Gow who had the biggest say in the closing minutes
The former Rangers forward chased a Lee Mair passback and although he looked unlikely to reach it, Samson slipped and the defender pulled Gow down for a penalty, which Hateley drilled into the bottom corner.
A minute later, the hosts made sure of maximum points when Gow latched onto Mark Reynolds' long ball, cut in from the left and sent the ball across the box where Murphy netted from close to the post.
Live text and stats
Saturday, 2 October 2010
Hateley (pen) 87
02 Saunders (Hammell 54)
07 Humphrey (Gow 75)
08 Jennings yellow card
11 Sutton (Forbes 70)
02 van Zanten
05 Mair yellow card
07 Murray yellow card
10 Higdon yellow card
18 Wardlaw yellow card
Ref: BrinesAtt: 4,384
Attempts on target
Attempts off target
90:00+3:16 The referee signals the end of the game.
90:00+2:48 Ross Forbes is ruled offside. Free kick taken by Craig Samson.
90:00+1:33 Short corner taken by Nick Blackman from the left by-line.
87:57 Assist by Alan Gow.
87:57 GOAL - Jamie Murphy:Motherwell 3 - 1 St Mirren Goal scored by Jamie Murphy from close in to the bottom right corner of the goal. Motherwell 3-1 St Mirren.
87:28 Free kick awarded for an unfair challenge on Paul McGowan by Ross Forbes. Free kick taken by Hugh Murray.
86:53 GOAL - Tom Hateley:Motherwell 2 - 1 St Mirren Tom Hateley scores a placed penalty. Motherwell 2-1 St Mirren.
85:50 Booking Lee Mair goes into the book for unsporting behaviour.
85:38 Penalty awarded for a foul by Lee Mair on Alan Gow.
83:31 Corner taken left-footed by Ross Forbes, clearance by Lee Mair.
82:33 David van Zanten challenges Nick Blackman unfairly and gives away a free kick. Shot comes in from Tom Hateley from the free
kick, blocked by David van Zanten.
82:06 Darren McGregor produces a right-footed shot from just outside the penalty area that goes harmlessly over the target.
81:17 Unfair challenge on Hugh Murray by Alan Gow results in a free kick. Hugh Murray takes the direct free kick.
79:08 Foul by Gareth Wardlaw on Darren Randolph, free kick awarded. Direct free kick taken by Darren Randolph.
78:44 Booking Caution for Gareth Wardlaw.
76:43 Gareth Wardlaw is adjudged to have handled the ball. Darren Randolph takes the direct free kick.
75:37 Stephen Craigan gives away a free kick for an unfair challenge on Gareth Wardlaw. The free kick is delivered right-footed
by Paul McGowan from left channel, Stephen Craigan makes a clearance.
74:55 Substitution Chris Humphrey leaves the field to be replaced by Alan Gow.
74:08 Foul by Hugh Murray on Keith Lasley, free kick awarded. Ross Forbes takes the free kick.
73:12 Stevie Hammell concedes a free kick for a foul on John Potter. Craig Samson restarts play with the free kick.
72:06 Stephen Craigan fouled by Michael Higdon, the ref awards a free kick. Direct free kick taken by Stevie Hammell.
71:36 Gareth Wardlaw produces a right-footed shot from just outside the penalty box that goes wide left of the target.
69:25 Substitution John Sutton goes off and Ross Forbes comes on.
69:12 Effort from outside the penalty box by Paul McGowan goes wide right of the goal.
68:32 Corner taken right-footed by Paul McGowan from the right by-line, Nick Blackman makes a clearance.
68:04 Paul McGowan takes a shot. Craig Samson makes a save.
66:18 Craig Samson restarts play with the free kick.
66:18 Booking Caution for Steve Jennings.
66:10 Steve Jennings gives away a free kick for an unfair challenge on Paul McGowan.
63:52 Assist on the goal came from Paul McGowan.
63:52 GOAL - Gareth Wardlaw:Motherwell 1 - 1 St Mirren Goal scored by Gareth Wardlaw from deep inside the penalty area to the top right corner of the goal. Motherwell 1-1 St Mirren.
62:47 Steve Jennings concedes a free kick for a foul on Gareth Wardlaw. Free kick crossed right-footed by Paul McGowan.
61:33 Shot from 25 yards by John Sutton. Craig Samson makes a save.
58:42 Effort on goal by Darren McGregor from a long way out goes over the bar.
57:54 Jamie Murphy takes a shot. Save by Craig Samson.
57:28 Lee Mair challenges John Sutton unfairly and gives away a free kick. Direct free kick taken by Nick Blackman.
56:35 Lee Mair concedes a free kick for a foul on Jamie Murphy. Steve Jennings takes the free kick.
55:23 Jamie Murphy has an effort at goal from 12 yards. Craig Samson makes a save.
54:50 Patrick Cregg concedes a free kick for a foul on Steve Jennings. Steve Jennings restarts play with the free kick.
53:23 Substitution Stevie Hammell joins the action as a substitute, replacing Steven Saunders.
51:31 Chris Humphrey concedes a free kick for a foul on Jure Travner. Jure Travner takes the free kick.
47:03 Free kick awarded for a foul by Patrick Cregg on Nick Blackman. Free kick taken by Darren Randolph.
45:49 Free kick awarded for an unfair challenge on Jamie Murphy by Hugh Murray. Steven Saunders takes the direct free kick.
45:01 The second half begins.
45:00+1:15 The referee calls an end to the first half.
45:00+0:27 Corner taken by Paul McGowan from the left by-line to the near post, Lee Mair takes a shot.
43:01 Shot by Tom Hateley from outside the box goes high over the target.
41:42 Foul by Darren McGregor on Nick Blackman, free kick awarded. Nick Blackman restarts play with the free kick.
39:44 Free kick awarded for an unfair challenge on Chris Humphrey by Jure Travner. Stephen Craigan restarts play with the free kick.
38:58 Close range headed effort by Gareth Wardlaw misses to the right of the goal.
38:30 Foul by Keith Lasley on Paul McGowan, free kick awarded. Hugh Murray restarts play with the free kick.
35:30 Effort from inside the area by Darren McGregor misses to the right of the goal.
34:22 Free kick awarded for a foul by Jamie Murphy on Lee Mair. Craig Samson takes the direct free kick.
31:50 Free kick awarded for an unfair challenge on Stephen Craigan by Michael Higdon. Darren Randolph restarts play with the free
31:05 John Sutton gives away a free kick for an unfair challenge on Hugh Murray. John Potter restarts play with the free kick.
29:26 Chris Humphrey takes a outswinging corner from the right by-line played to the near post, Unfair challenge on John Potter
by Nick Blackman results in a free kick. Free kick taken by Craig Samson.
27:27 Corner taken by Chris Humphrey from the left by-line, Michael Higdon makes a clearance.
27:08 Keith Lasley takes the chance to get an effort at goal. Patrick Cregg gets a block in.
26:36 Corner from left by-line taken by Chris Humphrey.
26:14 Corner taken right-footed by Chris Humphrey from the right by-line, clearance made by Hugh Murray.
25:54 Nick Blackman has a drilled shot. Save made by Craig Samson.
24:29 Paul McGowan takes a shot from 12 yards. Save made by Darren Randolph.
21:05 Unfair challenge on Tom Hateley by David van Zanten results in a free kick. Strike comes in from Tom Hateley from the free
kick, save by Craig Samson.
20:08 Effort from 18 yards by Chris Humphrey. Blocked by John Potter.
19:01 Shot from just outside the area by Jamie Murphy misses to the right of the target.
15:29 Free kick taken by Stephen Craigan.
15:29 Booking The referee shows Hugh Murray a yellow card.
15:20 Unfair challenge on Nick Blackman by Hugh Murray results in a free kick.
10:44 Stephen Craigan takes the direct free kick.
10:44 Booking Michael Higdon is booked.
10:36 Michael Higdon gives away a free kick for an unfair challenge on Keith Lasley.
8:12 Unfair challenge on Nick Blackman by Jure Travner results in a free kick. Stephen Craigan takes the direct free kick.
2:32 GOAL - Chris Humphrey:Motherwell 1 - 0 St Mirren Chris Humphrey finds the net with a goal from just outside the box to the top right corner of the goal. Motherwell 1-0 St
1:57 Michael Higdon gives away a free kick for an unfair challenge on Steve Jennings. Tom Hateley takes the direct free kick.
0:48 Nick Blackman challenges Darren McGregor unfairly and gives away a free kick. Craig Samson restarts play with the free kick.
0:17 Gareth Wardlaw takes a shot. Darren Randolph makes a save.
0:00 The ref blows the whistle to begin the match.
Live text and data provided by The Press Association.
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