Celtic leapfrogged Kilmarnock to the top of the Ladbrokes Premiership with a stunning victory in their clash at Parkhead.
Steve Clarke's side travelled to Glasgow with a one-point lead over both Rangers and their Old Firm rivals but their much-talked about title credentials were first tested in the fifth minute when winger James Forrest swept the home side into the lead with a well-taken drive.
Further goals before the break from striker Odsonne Edouard, captain Mikael Lustig and midfielder Ryan Christie provided a reality check for the visitors.
Substitute Eamonn Brophy, on for Aaron Tshibola for the second half, reduced the deficit with a penalty in the 52nd minute, but Forrest grabbed his second to register Brendan Rodgers' first win over Clarke in five attempts in Scottish football after two draws and two Killie wins previously.
As well as taking Celtic two points clear of Kilmarnock at the top with two games in hand over the Rugby Park club - Rangers can go back top with a high-scoring win at Dundee on Sunday - the result and performance was a huge boost ahead of the do-or-die Europa League clash against Salzburg at Parkhead on Thursday night.
The visitors were handed a lesson in the first 45 minutes and they were still working their way into the game when Emilio Izaguirre's cross from the left touchline was swept in on the half-volley by Scotland winger Forrest from 12 yards.
The home side looked in the mood and minutes later Killie keeper Daniel Bachmann moved smartly to prevent a second when his defender Scott Boyd miscued a clearance before he blocked a close-range shot from Tom Rogic after he had been cleverly played in by Christie.
Killie, however, were caught out again in the 25th minute when another incisive Celtic attack through middle saw Rogic play in Edouard and the French striker confidently knocked the ball past Bachmann from 14 yards.
Rampant Celtic went looking for more goals and in the 36th minute the third arrived when midfielder Callum McGregor's free-kick from the left was volleyed in by Lustig from eight yards out.
Killie were being made to suffer.
Christie curled in the fourth with a 25-yard free-kick seconds before the break and the home side were given a deserved standing ovation going up the tunnel.
Seven minutes after the break Celtic defender Filip Benkovic was judged by referee Nick Walsh to have fouled attacker McKenzie inside the box and Brophy slammed the penalty past keeper Craig Gordon, who got a hand to the ball but could not keep it out.
Forrest then made his mark again. The in-form winger was unfortunate when his side-footed shot rebounded off the post but in the 67th minute he slammed in his second from an angle when the ball broke loose after Bachmann had thwarted Christie.
Both sides kept going for more goals which continued the excitement and in the 70th minute winger Scott Sinclair curled the ball against the junction of bar and post from the edge of the box, before he missed a good chance he had created for himself.
There was to be no more Celtic goals but it was a convincing win against a Killie team who found out the hard way about title-winning standards.