Dundee United never looked in this game form the opening seconds. Celtic came out full of ambition and took the game to United immediately, gaining four corners in the opening few minutes. Meanwhile it took United half an hour to threaten Celtic's goal, and then only from a free kick by Griffin.
Celtic eventually took a deserved lead on 41 minutes through Petrov, after being played through by Henrik Larsson.
The second half was a continuation of the first, with Celtic dominating from the outset, and United rarely looked like taking what would have been an undeserved point.
There is one game to go before the split now, and this defeat makes it impossible for United to make the top half of the table.