Leaders Celtic lost their first Scottish Premiership match of the season as closest rivals Aberdeen beat them for the second time in two weeks. The champions never recovered from the loss of Dutch central defender Virgil van Dijk who was shown a straight red card on 12 minutes for a bad foul.
But any thoughts of a closer battle at the top of the table will have to wait – Celtic's lead over Aberdeen is now down to a mere 21 points.
The Dons, who won 2-1 at Celtic in the Scottish Cup on February 8, capitalised on their numerical advantage with two goals in four minutes just before half-time. The first, on 41 minutes, was scored by Jonathan Hayes with a left-foot shot from outside the area into the top left corner of the Celtic goal. The winner came on 45 minutes when a cross from Niall McGinn was met in the six-yard-box by the head of Adam Rooney.
Celtic had struggled to produced a shot on target in the first half. Anthony Stokes went close early on and Israeli midfielder Nir Biton saw his 38th-minute close-range shot saved by the Aberdeen keeper Jamie Langfield.
Manager Neil Lennon replaced Kris Commons with the 22-year-old winger James Forrest for the start of the second half as Celtic chased the goal that would get them back into the game. And on 62 minutes the change paid off as Leigh Griffiths found Forrest in the area, and the new arrival scored with a fierce shot to the top corner.
But though Celtic pushed for an equaliser, bringing on strikers Georgios Samaras and Amido Baldé, and Stokes saw a shot saved, Aberdeen held on for another famous win.