The Hoops make the trip to McDiarmid Park 24 hours before second place Aberdeen face Hamilton.
It is their last match before the Glasgow giants host Inter Milan in the first leg of their last 32 Europa Cup tie and Ronny Deila may be tempted to utilise his squad for the encounter with St Johnstone.
Celtic will be missing Kris Commons and Mikel Lustig for the match in Perth but were handed a boost in midweek when new signings Stuart Armstrong and Gary Mackay-Steven scored on their debuts.
And Mackay-Steven is keen to play his way into the manager's plans ahead of their crucial European tie.
"I have confidence in my ability
I know what I can do and just want to show it in every game," the winger said.
"If you get the nod to play the standard of player here is so high you need to take your chance
You need to prove to the manager you can play at this level.
"Hopefully I did that but there are so many quality players at this club and the bench is really strong.
"It's great for the manager and keeps everyone on their toes."
Manager Deila was delighted with the impact the transfer deadline signings from Dundee United made in their first match and says competition for places is high at the club.
"I think it pushes the process forward quicker because you can tell them things and they think they understand what you are saying, but maybe it's not right and you see others coming in and pushing them," the Celtic manager said.
"They need to make the changes they need to make or they will struggle to get into the team but there is a team spirit and I'm very into understanding that everybody is important.
"We will make each other good, if someone is out of the team it's not a bad thing, it's just that another player suits just now while the other one has played too much.
"They have to understand that we have important games coming all the time and they have to think of themselves and be as fit and as ready as possible when they play."
Celtic, who have won their past seven matches in all competitions, take on a St Johnstone side with just one win out of six and who last week crashed out of the Scottish Cup to Championship side Queen of the South.
Elsewhere on Saturday, caretaker manager Gary Locke takes charge of Kilmarnock for the first time as they take on Dundee United at Rugby Park, Dundee host Partick Thistle at Dens Park, St Mirren take on Inverness Caledonian Thistle and bottom of the table Ross County welcome fellow strugglers Motherwell to Victoria Park.
Fixtures (1500 unless otherwise stated)
Saturday
St Johnstone v Celtic (1245)
Dundee v Partick Thistle
Kilmarnock v Dundee United
Ross County v Motherwell
St Mirren v Inverness CT
Sunday
Hamilton v Aberdeen (1530)
Source : AFP
Source: AFP