The Hoops crashed out at the last-32 stage of the competition on Thursday night after a 3-1 home defeat by FC Copenhagen resulted in a 4-2 aggregate scoreline.
It was a night of frustration for the Celtic boss who viewed it as a lost opportunity and he is looking for his side to make amends and take the next step to retaining the William Hill Scottish Cup in the quarter-final at McDiarmid Park.
Lennon said: "St Johnstone are in good form at home.
"They have turned their season around quite a bit and we know it is a difficult place to go.
"I am hoping I get a reaction from my players from last night and I am sure I will.
"I hope they are angry and if they play angry they can be very good.
"So, we will get them in on Saturday and get their minds refocused again on trying to retain the cup."
Lennon left Celtic Park on Thursday night wondering how his side, who should have had the tie finished in the first leg at the Parken Stadium last week where instead they left with a 1-1 draw, failed to finish off the job in Glasgow.
Striker Odsonne Edouard levelled with a VAR-awarded penalty in the 82nd minute and it looked like the match had swung back towards the home side.
However, just three minutes later, midfielder Pep Biel restored the visitors' lead before striker Dame N'Doye, who scored in Denmark last week, added a third to seal a miserable night for the triple treble winners.
Former Celtic captain Lennon said: "Any next game would be a pick up after last night.
"It is just bitterly disappointing that we threw it away in the last five minutes.
"To score and then lose a goal two minutes later was inexcusable really from our point of view.
"I just look at the next game and we will see who is fit and available and see who is ready to play and we will go out there and try to win the game as best we can."