St Johnstone improved on the calamitous, mistake-filled performance against Livingston seven days ago but it was back to back Premiership defeats for Callum Davidson’s men nonetheless.
Had they been at last season’s best it would have been an intriguing contest as the Saints game plan of staying compact and making it hard for Celtic to play through them worked pretty well for over half an hour.
It was undone on 36 minutes, though, when Callum Booth misjudged the flight of a Josip Juranovic shot.
That allowed ex-Saint Anthony Ralston the opportunity to deliver the ball across the six-yard line where he found Georgios Giakoumis, who gave Zander Clark no chance with his first-time finish.
Result never in doubt
From then on the result was never in any great doubt.
Ali Crawford made a superb sliding tackle to prevent Jota making it 2-0 in the second half.
But Celtic got their second when Liam Gordon brought down Kyogo Furuhashi just inside the box and Juranovic made no mistake from the penalty spot.
With Gordon back in the team, as well as Craig Bryson, Saints will now attempt to finish the first quarter of the season with a much-needed victory against Hearts in midweek.
