A 92nd minute David Watson stunner gave Kilmarnock their first away league win of the season, and their first win in Aberdeen since 2018, consigning the Dons to 11th in the league.
Barry Robson, who was appointed permanent Aberdeen manager in May, became the first Dons boss to lose consecutive games against the Ayrshire side since Mark McGhee in 2010.
Whilst he led the Dons to third in the league last season, a run of 13 points from 14 league games has sent the Pittodrie club to the play-off spot. They have claimed just four points from their last six league games.
For comparison, Jim Goodwin claimed 16 points from his final 14 league games in charge of the Dons, three more than the Dons have managed under Robson this season.
Robson has said his side must “pick up points” from the next few games, starting with Hearts at the weekend.
Killie, meanwhile, claimed their first away win of the campaign, and third since their promotion 18 months ago, to climb back into the top six.
The Rugby Park side having managed three wins over Aberdeen in the last 12 months, as many as they’d managed in the previous 12 years.
Young midfielder David Watson continued his fine form by score only his second Premiership goal for the club.
Recently signing a contract extension until 2026, the youngster has caught the eye of many fans across Scotland.
His manager, Derek McInnes, is full of praise of the 18-year-old. He said that Watson does shooting drills in training, but his winning goal was “all instinct” and nothing like what they’ve trained him to do.
However, Watson will be unavailable for their home game against Celtic on Sunday, due to accumulating six yellow cards this season.
Aberdeen are back at home on Saturday at 3pm against Hearts in a massive crunch game for Barry Robson. Kilmarnock, meanwhile, host Celtic on Sunday at 12pm, as they look to repeat their August Viaplay Cup win over the reigning champions.