Saints welcome Celtic to McDiarmid Park on Sunday in the Ladbrokes Premiership, with Brendan Rodgers' side making their second trip to Perth this season.
The club's met just over a week ago in the Betfred Cup quarter-final when Celtic managed to secure a 1-0 victory over Tommy Wright's men.
The visitors defeated Aberdeen last weekend and sit in fifth place, while Saints went down 2-1 to top of the table Hearts at Tynecastle. The Hoops were also in Europa League action midweek suffering a 3-1 defeat in Salzburg.
Looking ahead to Sunday's match, the manager is looking to build on the performance of his players from the last time Celtic visited McDiarmid Park.
"We're looking forward to testing ourselves again on Sunday against a very good Celtic side," Tommy said.
"We've had a full week of training and over the past few days we've been working on specifics in terms of how we can better what was actually a good performance against Celtic in the Betfred Cup.
"Our record against the bigger teams is actually pretty good so hopefully we can add to that this weekend.
"When you come up against teams with the players and quality of Celtic you have to be prepared to be without the ball at times. It's getting the balance right.
"We've lost our last two games by a one-goal margain and on another day we might have sneaked something from both. There is a lot of belief in the squad that we can get something on Sunday."
Striker Tony Watt started on the bench against Hearts last weekend, and Tommy is still to make a decision on whether the 24-year-old is fit enough to start on Sunday.
"Tony has trained this week and his injury is manageable," the managed said.
"He'll definitely be in the squad for the weekend but we'll assess him closer to kick-off to see if he's ready to start the match.
"Murray Davidson is also back in training but the game has probably come too soon for him. The last thing we'd want to do is risk him breaking down and setting him back.
"The good news is Murray should be fit for Motherwell next weekend. Brian Easton is our only other absentee and we're working hard to get him back available to us as soon as possible."
Supporters are reminded that Sunday's match is a 3:30PM kick-off.
As announced earlier this season, St. Johnstone Season Ticket holders can 'Bring a Friend for a Tenner' to Ladbrokes Premiership matches against Celtic and Rangers at McDiarmid Park during the 2018/19 campaign.
Season Ticket holders looking to take advantage of this offer against Celtic at the weekend are reminded that they MUST pre-purchase a ticket for the match, and cannot pay £10 at the turnstiles.
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