Manager Brendan Rodgers praised Celtic's "persistence and quality" after two late goals at St Johnstone took them back six points clear of Rangers at the top of the Ladbrokes Premiership.
When it looked like Saints might just hold out for a draw, winger James Forrest broke the deadlock in the 78th minute before Timothy Weah, on for injured fellow substitute Odsonne Edouard, clinched the win with an 89th-minute finish.
Hoops defender Kristoffer Ajer was then sent off by referee Willie Collum for preventing Saints substitute Callum Hendry making his way towards the Celtic goal.
Rodgers, whose side had beaten St Johnstone 2-0 at Parkhead on Wednesday night, said: "It was a good demonstration of our persistence and quality in the game.
"It was a very good performance against a team that are so difficult to play against. We had everything thrown at us today in terms of injuries and what not.
"The game went how we thought it would go, similar to Wednesday night where we had to be patient while playing with the intensity. We had really good tempo in our game.
"We created chances and kept a clean sheet which is really important."
Rodgers – already without Kieran Tierney, Dedryck Boyata, Leigh Griffiths, Tom Rogic, Olivier Ntcham, Tony Ralston and Filip Benkovic for various reasons – will have to assess what he has at his disposal before Wednesday night's home game against Hibernian.
Right-back Mikael Lustig stayed in at the interval with an Achilles problem, leaving new singing Jeremy Toljan to make his debut.
Edouard, who had replaced Oliver Burke, was taken away on a stretcher after being injured in a challenge from Saints skipper Joe Shaughnessy a yard from goal.
Forrest went off with a tight hamstring leaving the Hoops with 10 men and Ajer will be suspended for the Hibs game.
Rodgers, who had no complaints about Ajer's dismissal, said: "If you watch the replay again the boy Shaughnessy's stretching and his foot is accidental as Odsonne's gone to hit it.
"These modern boots are not so tough. It's just caught him right on the front of his foot so he's in a wee bit of pain but hopefully he will be okay.
"James is more of a worry, he felt his hamstring a bit tight. We had to play the last 10 minutes or so with 10 men. It was Ryan's ribs. He got a bang on the ribs, he could hardly breathe.
"Thankfully we added to the squad, which we needed to do, and we'll get some players back hopefully.
"We'll make do. We have some outstanding players who can play in those positions. We will assess it on Monday and see where we're at."
St Johnstone boss Tommy Wright, who has to prepare his side to face Celtic in the William Hill Scottish Cup next Sunday after a trip to Hamilton on Wednesday, noted improvement from the defeat at Parkhead.
"I'm obviously disappointed with the result again," he said. "But I asked for an improved performance and I thought I got that, especially in the first half.
"There were moments when we should have capitalised but we didn't do it.
"I thought we had weathered the storm but we made a mistake for the all-important first goal and then we are chasing the game.
"They then caught us on the counter but there are more positives today than Wednesday. It's still another defeat and we have to move on to midweek."
