Dundee United were top dogs in the Tayside derby, blowing St Johnstone away with a clinical first half performance.
Keith Watson's deflected shot and David Goodwillie's header put the hosts in control.
And Gary Mackay-Steven opened his account for the season before the interval.
The visitors' misery continued in the second half with Stuart Armstrong firing United's fourth.
For a St Johnstone side that had looked defensively robust in their opening games the result is a shock, with United displaying an energy and assuredness of movement throughout which augurs well for the season ahead.
Watson curled a fierce shot past goalkeeper Steve Banks from 22 yards, with the ball taking a nick off a Saints defender en route to goal.
But the visitors hit back with a Stevie May header just over the bar.
The Perth side enjoyed a good spell of pressure but they were gradually thrown onto the back foot by the home side's tempo and rhythm.
Goodwillie latched on to Calum Butcher's headed pass to nod home - his first goal since rejoining the Tangerines on loan from Blackburn Rovers.
Banks then made a stunning save from a deflected Goodwillie shot that had appeared to be looping into the net before the keeper acrobatically tipped away.
However, the home side claimed a third time when Andrew Robertson raced down the left and slipped the ball through to Gary Mackay-Steven, who prodded the ball under Banks.
Nigel Hasselbaink went close from six yards after the restart, home keeper Radoslaw Cierznak blocking with his feet.
And Jackie McNamara's side soon extended their advantage. Gary Mackay-Steven's lay-off found Stuart Armstrong, whose shot took a slight deflection over Banks into the net.
Steven MacLean should have immediately pulled one back for St Johnstone but hooked his shot over.
United substitute Nadir Ciftci cracked a low shot goalwards but Banks threw himself low to his right to push the ball to safety.
Ciftci then raced through one-on-one with Banks but the keeper's trailing leg saved a seemingly certain fifth goal.
Live Text Commentary
Full Time The referee blows the whistle to end the game.88:58 Booking
Frazer Wright receives a yellow card.88:42
Free kick taken by John Rankin.88:04
Unfair challenge on Ryan Gauld by Frazer Wright results in a free kick.86:47
Corner from the left by-line taken by Ryan Gauld.83:47
David Mackay sends in a cross.83:35
John Rankin makes a clearance.83:29
Chris Millar crosses the ball.83:17
Clearance made by Andrew Robertson.82:58
David Wotherspoon restarts play with the free kick.82:44
Free kick awarded for a foul by John Rankin on Stevie May.82:09
David Mackay makes a clearance.81:43
Nadir Ciftci takes the chance to get an effort at goal. A parry by Steve Banks prevents the goal.80:34
Keith Watson makes a clearance.80:22
Corner from the left by-line taken by David Wotherspoon.78:45 Substitution
Substitution Chris Erskine on for David Goodwillie.77:25
Corner taken by Ryan Gauld.77:13
Clearance by Steven Anderson.77:09
Corner taken by Ryan Gauld from the right by-line.
Substitution Ryan Gauld replaces Stuart Armstrong.74:27 Substitution
Substitution Nadir Ciftci comes on in place of Ryan Dow.72:45
Header by Steven MacLean goes over the bar.72:40
Gwion Edwards produces a cross.70:00 Substitution
Substitution Nigel Hasselbaink leaves the field to be replaced by Gwion Edwards.69:26
Clearance made by Frazer Wright.69:11
Corner taken by Ryan Dow from the right by-line.67:53
Tom Scobbie takes the free kick.67:37
Paul Paton challenges Gary McDonald unfairly and gives away a free kick.67:24
Shot by John Rankin went over.66:13
David Wotherspoon restarts play with the free kick.66:05
Free kick awarded for an unfair challenge on David Wotherspoon by Paul Paton.64:36
Clearance made by David Wotherspoon.64:30
The ball is sent over by Paul Paton.62:17 Substitution
Substitution Gary McDonald is brought on as a substitute for Murray Davidson.62:04
Corner taken by David Wotherspoon.61:40
The ball is sent over by Stevie May.57:22
Steven MacLean takes a shot and goes over the bar.56:56
Chris Millar restarts play with the free kick.56:47 Booking
The referee books Gary Mackay-Steven for unsporting behaviour.56:41
Gary Mackay-Steven challenges Murray Davidson unfairly and gives away a free kick.54:18
John Rankin takes the free kick.54:10
Chris Millar is given a yellow card.54:10 Booking
Chris Millar concedes a free kick for a foul on Andrew Robertson.52:49
The assist for the goal came from Gary Mackay-Steven.52:49 Goal scored
Goal! - Stuart Armstrong - Dundee U 4 - 0 St J'stone Stuart Armstrong grabs a goal with a right foot finish. Dundee Utd 4-0 St Johnstone.51:13
The ball is sent over by Murray Davidson.49:52
Clearance made by Sean Dillon.49:40
Corner taken by David Wotherspoon.49:10
Nigel Hasselbaink has an effort at goal. Radoslaw Cierzniak parries the effort to safety.47:24
Ryan Dow takes a strike on goal from the free kick which goes harmlessly over the bar.46:52
Foul by Chris Millar on Ryan Dow, free kick awarded.45:01
The second half begins.45:01 Substitution
Substitution Chris Millar comes on in place of Patrick Cregg.45:00 +1:26 Half time
Half Time It is the end of the first-half.45:00 +1:06
Shot by David Goodwillie went wide right of the target.44:58
Radoslaw Cierzniak restarts play with the free kick.44:49
Steven MacLean challenges Paul Paton unfairly and gives away a free kick.44:21
Steve Banks restarts play with the free kick.44:14
Foul by John Rankin on Stevie May, free kick awarded.44:05
Corner taken by Ryan Dow.43:48
Clearance made by Murray Davidson.43:30
Corner taken by Ryan Dow.41:28
Keith Watson restarts play with the free kick.41:19
Unfair challenge on Gary Mackay-Steven by Patrick Cregg results in a free kick.40:42
Paul Paton manages to make a clearance.40:37
Stevie May takes the free kick.40:13
John Rankin gives away a free kick for an unfair challenge on Stevie May.39:34
The assist for the goal came from Andrew Robertson.39:34 Goal scored
Goal! - Gary Mackay-Steven - Dundee U 3 - 0 St J'stone Gary Mackay-Steven slots the ball left footed into the goal. Dundee Utd 3-0 St Johnstone.36:46
Free kick taken by Steve Banks.36:43
The referee blows for offside against Gary Mackay-Steven.35:11
Centre by Nigel Hasselbaink.34:13
Paul Paton manages to make a clearance.34:00
Free kick crossed by Tom Scobbie.33:38
Free kick awarded for a foul by Keith Watson on Steven MacLean.32:13
Frazer Wright manages to make a clearance.32:03
Corner taken by Ryan Dow.29:08
Murray Davidson manages to make a clearance.28:52
Corner taken by Ryan Dow from the right by-line.28:26
Corner from the left by-line taken by Ryan Dow.27:45
Corner from the left by-line taken by Ryan Dow.27:03
David Goodwillie takes the chance to get an effort at goal. Steve Banks parries the effort to safety.26:37
Clearance by Keith Watson.26:29
Free kick crossed by David Wotherspoon.25:58
Andrew Robertson gives away a free kick for an unfair challenge on David Mackay.24:53
The assist for the goal came from Keith Watson.24:53 Goal scored
Goal! - David Goodwillie - Dundee U 2 - 0 St J'stone David Goodwillie scores with a header. Dundee Utd 2-0 St Johnstone.24:18
Free kick crossed by Ryan Dow.24:02
Foul by Patrick Cregg on Gary Mackay-Steven, free kick awarded.23:21
Steve Banks takes the free kick.23:07
Foul by Andrew Robertson on Murray Davidson, free kick awarded.22:38
Corner taken by David Wotherspoon from the left by-line.18:59
David Mackay restarts play with the free kick.18:47
Booking for Ryan Dow for unsporting behaviour.18:47 Booking
David Mackay fouled by Ryan Dow, the ref awards a free kick.17:47
Paul Paton manages to make a clearance.17:32
Corner taken by David Wotherspoon.14:53
Corner from the left by-line taken by David Wotherspoon.14:34
Nigel Hasselbaink sends in a cross.14:05
Steve Banks restarts play with the free kick.13:57
Ryan Dow concedes a free kick for a foul on Tom Scobbie.13:01
Free kick taken by Paul Paton.12:49
Paul Paton fouled by Murray Davidson, the ref awards a free kick.8:34
The ball is swung over by Nigel Hasselbaink.7:26
Header by Stevie May goes over the bar.5:45
Paul Paton has an effort at goal and missed to the left of the net.3:02
Assist on the goal came from John Rankin.3:02 Goal scored
Goal! - Keith Watson - Dundee U 1 - 0 St J'stone Keith Watson scores with their left foot. Dundee Utd 1-0 St Johnstone.0:00
The referee gets the match started.
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