David Turnbull's comeback could not inspire Motherwell as they fell to a 2-1 defeat at St Mirren.
Ten-man Aberdeen were beaten 2-1 by Ross County to fall to fourth in the Ladbrokes Premiership.
Motherwell defender Jake Carroll will miss at least the remainder of the season after suffering an Achilles injury during Tuesday's Scottish Cup defeat at St Mirren.
Rangers' match against Livingston at Ibrox is among two Scottish Premiership games postponed due to a waterlogged pitch amid Storm Dennis.
A round-up of Wednesday's Scottish Premiership action as St Johnstone leave it late to beat 10-man Motherwell.
Kris Boyd believes Odsonne Edouard is good enough to play in any league in the world and says it is vital he stays fit if Celtic are to maintain form.
Scottish Cup holders Celtic will travel to St Johnstone in the quarter-finals of this year's competition.
Celtic's comprehensive 4-0 win over Motherwell kept the champions on a steady course for their ninth successive Scottish Premiership title.
| # | Team | Pl | GD | Pts |
|---|---|---|---|---|
| 1 | Celtic | 28 | 65 | 76 |
| 2 | Rangers | 27 | 45 | 64 |
| 3 | Motherwell | 28 | 0 | 42 |
| 4 | Aberdeen | 28 | 2 | 41 |
| 5 | Livingston | 28 | 3 | 38 |
| # | Team | Pl | GD | Pts |
|---|---|---|---|---|
| 1 | Motherwell | 4 | 13 | 12 |
| 2 | Morton | 4 | 6 | 8 |
| 3 | Q of South | 4 | 0 | 6 |
| 4 | Dumbarton | 4 | -9 | 3 |
| 5 | Annan | 4 | -10 | 1 |
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