A second-half high on substitutions and low on chances. Brendan Rodgers will not be too perturbed that his men have taken their foot off the gas with that crucial Champions League play-off second leg against Hapoel Beer Sheva coming up in Israel on Tuesday.

The champions coasting to the three points.

Brendan Rodgers makes his third and final change, replacing goalscorer James Forrest with Ryan Christie.

Richard Foster dives to intercept Kieran Tierney's cross but almost heads the ball into his own net.

Saints clear the danger from the subsequent corner.

Chris Kane replaces David Wotherspoon for St Johnstone.

Former Rangers & Scotland striker Steven Thompson on Radio Scotland: "Nir Bitton didn't need to get involved there.  It is a stupid booking."

Moments after being booked, Nir Bitton departs the scene to be replaced by Liam Henderson.

Murray Davidson booked for a poor challenge on Saidy Janko. Nir Bitton remonstrates with Davidson and also finds himself with a yellow card to his name.

Both sides make their first changes as St Johnstone introduce Liam Craig for Blair Alston as Moussa Dembele replaces Leigh Griffiths for Celtic.

Tom Rogic seems to be growing in stature every time he pulls on the Celtic jersey.

The Australian midfielder lets rip with a powerful drive from 20 yards which beats Alan Mannus all ends up, but the ball crashes back off the crossbar.

Should Leigh Griffiths lead Scotland's attack in the upcoming World Cup qualifying campaign?

We are back underway at McDiarmid Park.

Leigh Griffiths was booked by referee Craig Thomson for simulation so the SFA can not impose any retrospective punishment.

Image source, SNS

He was on fire last season, he is still on fire this season and he has scored again today. So should Leigh Griffiths spearhead Scotland's upcoming World Cup qualifying campaign?

Tweet us @BBCSportScot or tweet me @BBCAndyBurke. Or just use the hashtag #BBCSportScot.

Image source, SNS

Tom English
BBC Sport Scotland at McDiarmid Park

"Celtic's speed of thought and speed of attack is like chalk and cheese compared to last year. Turnover in midfield and suddenly St Johnstone are hopelessly out-numbered. Three goals clear. And good value for it."

Former Rangers & Scotland striker Steven Thompson on Radio Scotland: "It is abysmal defending from St Johnstone.  Brad McKay was trying to usher the ball out on the touchline but he was absolutely bullied by Leigh Griffiths. James Forrest still had a lot to do and it is a fantastic finish, but that is really poor from Saints.  It is a makeshift back four and they are defending like a makeshift back four."   

Pat Bonner
BBC Radio Scotland pundit at McDiarmid Park

"Alan Mannus must be thinking 'Where are my defenders?' (for the second Celtic goal).  He has made two brilliant saves and but none of his defenders were around to deal with the rebounds."  

Three goals in 16 minutes have done the damage as Celtic threaten to run riot at McDiarmid Park.

Leigh Griffiths got the ball rolling with a close range finish before Scott Sinclair doubled the lead.

James Forrest's wonderful solo goal put the champions on easy street. 

Looks like a damage limitation job for the home side in the second half.

The resulting free-kick is fired towards goal by Leigh Griffiths but Alan Mannus gets a strong hand behind it to push the ball away.