Motherwell gained revenge for their Scottish Cup quarter-final defeat by Aberdeen thanks to Stevie Hammell's long-range thunderbolt.
Well must also beat Kilmarnock at Rugby Park next weekend to prevent Celtic being able to clinch the title away to Rangers the following day.
Hammell fired home from 35 yards after 22 minutes at Fir Park.
Aberdeen's Jason Brown was the busier goalkeeper, with Darren Randolph only called upon once to save.
And the deserved victory lifts Stuart McCall's side level with second-top Rangers, who were docked 10 points for going into administration but have a superior goal difference.
Defeat for the Dons on the same ground as last week's 2-1 Cup win ended their unbeaten run of 13 games in all competitions and leaves Craig Brown's side six points adrift of Hearts in the race to finish in the top half of the table before the Scottish Premier League splits into two.
Motherwell had been forced to hand Adam Cummins, 14 days after his 19th birthday, a debut in a defence decimated by suspensions for Shaun Hutchinson and Tim Clancy, plus captain Stephen Craigan's niggling injury.
Cummins' youth squad team-mate, Stuart Carswell, was given his second start in midfield against an Aberdeen side who were able to add the experience of Gavin Rae and Chris Clark.
It was the Dons who started in slightly more cohesive fashion, with the two managers switching their formations in an attempt to wrong-foot their counterpart in light of a familiarity resulting from last weekend's Cup meeting.
However, Aberdeen were fortunate that referee Iain Brines ruled that Andrew Considine was not the last man when the defender's hauling down of Henrik Ojamaa resulted in a yellow card instead of red.
The Estonian striker set up the opening goal soon after, his ball into the path of Hammell allowing the defender to fire high into the corner of the net from all of 35 yards.
Only an excellent save from Brown prevented Carswell scoring his first senior goal after Brines allowed play to progress after a foul by the already-booked Considine, who was testing the referee's patience.
Brown rescued the Dons again when Steve Jennings directed a header powerfullly towards the top corner.
Considine fired a couple of yards over as Aberdeen finally threatened the Motherwell goal just in time to beat the half-time whistle.
However, it was back with the home side in the ascendency immediately after the break when Carswell's low, 20-yard drive forced a save from Brown.
The Dons were struggling to create chances but had two in quick succession after Scott Vernon's side-footed effort forced Randolph to turn the ball over the crossbar and Rory Fallon headed just too high from the resulting corner.