Match ends, St. Johnstone 2, Celtic 1.
St Johnstone came from behind to beat champions Celtic and secure a fourth-place Premiership finish.
Leigh Griffiths' solo effort put the visitors ahead at McDiarmid Park, taking his tally for the season to 40.
A howler from Stefan Johansen allowed Steven MacLean in to level with a neat finish.
Efe Ambrose made another costly mistake, colliding with goalkeeper Logan Bailly to allow Graham Cummins to stab in the winner.
With the title secured, Celtic boss Ronny Deila made seven changes to the side that beat Aberdeen 3-2 at Parkhead on Sunday, but paid the price with a fourth league defeat of the season.
Craig Gordon, Charlie Mulgrew and Mikael Lustig were given the night off, with Nir Biton, Stuart Armstrong, Tom Rogic and Keiran Tierney dropping to the bench.
The travelling Celtic supporters were given a rare glimpse of Scott Allan, Ryan Christie, Saidy Janko and Belgian goalkeeper Bailly among the replacements.
Bailly was busy enough in the early exchanges as St Johnstone found a lot of joy down their right, where Emilio Izaguirre was playing what might prove to be his last game for the champions given Tierney's form.
The goalkeeper had a few testing crosses to deal with in the first few minutes but it was Saints' last line of defence that kept the scoreline level when the visitors finally clicked going forward.
Clark denied Griffiths with a fine save just when Scotland's top marksman seemed certain to convert an inviting cross following intelligent set-up play from Christie.
That was a rare moment of anxiety for Tommy Wright's side as they dominated possession for long spells of the first half as Celtic found it hard to produce any fluent attacking football.
Their increased tempo early in the second paid off with another sublime goal from Griffiths.
There seemed little danger when he picked up possession at the left edge of box but he weaved past two challenges before stabbing a left-foot shot beyond the onrushing Clark, his 31st league goal.
St Johnstone were gifted the chance of a quick equaliser in the 55th minute when Johansen was caught in possession on the edge of his own penalty area and veteran striker MacLean finished with aplomb.
The game looked to be drifting towards a draw before Ambrose tangled with Bailly and Cummins tapped home to make it four straight post-split wins for Tommy Wright's side.
- 6AndersonBooked at 35mins
- 16SwansonBooked at 61minsSubstituted forDoyleat 90'minutes
- 9MacLeanBooked at 57mins
- 25KaneSubstituted forCumminsat 59'minutes
- 22JankoSubstituted forRalstonat 74'minutes
- 25JohansenBooked at 28minsSubstituted forBittonat 66'minutes
- 19AllanSubstituted forRogicat 80'minutes
- William Collum
- Shots on Target
Second Half ends, St. Johnstone 2, Celtic 1.
Attempt saved. Ryan Christie (Celtic) right footed shot from the centre of the box is saved in the centre of the goal.
Substitution, St. Johnstone. Michael Doyle replaces Danny Swanson.
Foul by Steven MacLean (St. Johnstone).
Nir Bitton (Celtic) wins a free kick on the left wing.
Attempt missed. Graham Cummins (St. Johnstone) header from the centre of the box is close, but misses to the right.
Attempt missed. Callum McGregor (Celtic) right footed shot from outside the box is close, but misses to the left.
Substitution, Celtic. Tomas Rogic replaces Scott Allan.
Goal! St. Johnstone 2, Celtic 1. Graham Cummins (St. Johnstone) right footed shot from very close range to the centre of the goal.
Substitution, Celtic. Anthony Ralston replaces Saidy Janko.
Attempt missed. Nir Bitton (Celtic) right footed shot from outside the box misses to the right.
Steven MacLean (St. Johnstone) wins a free kick in the attacking half.
Foul by Nir Bitton (Celtic).
Substitution, Celtic. Nir Bitton replaces Stefan Johansen.
Attempt missed. Danny Swanson (St. Johnstone) left footed shot from the left side of the box is close, but misses to the left.
Attempt saved. Ryan Christie (Celtic) left footed shot from outside the box is saved in the centre of the goal.
Danny Swanson (St. Johnstone) is shown the yellow card for a bad foul.
Foul by Danny Swanson (St. Johnstone).
Saidy Janko (Celtic) wins a free kick in the defensive half.