Victory, but at a cost.

What threatened to be a frustrating afternoon for Celtic in Perthshire ended with little immediate threat to the club’s six-point lead at the top of the table but there was collateral damage along the way.

Forced to finish the game with 9-men following what appeared to be a hamstring injury to James Forrest after he finally burst the dam with the opening goal 12 minutes from time, a late red card for Kristoffer Ajer for pulling back Callum Hendry compounded Celtic’s current personnel problems.

By the time that Forrest pulled up, Odsonne Edouard had already been forced off after just eight minutes of involvement after feeling the boot of Joe Shaughnessy and all three subs had been used.

While there relief at the two late goals and applause for the contribution of star turn Timo Weah who came off the bench to set up one and score one, there will be a feeling that Celtic do not have their problems to seek ahead of a busy month.

The Parkhead side host Hibs on Wednesday evening, St Johnstone again on Sunday and then have Valencia in the opening leg of the Europa League the following week. At the minute the injury list is extensive; Dedryck Boyata is on the cusp of a return to training but Filip Benkovic, Edouard, Forrest, Kieran Tierney, Tom Rogic, Olivier Ntcham, Leigh Griffiths are all out while Ajer will miss the midweek game through suspension. Mikael Lustig also had to make way at the break yesterday for new arrival Jeremy Toljan as the Swede was toiling with an achilles injury.

If there were headaches to take away from the game, there were also the performance of Weah for Rodgers to enjoy. The 18-year-old has netted three goals in five appearances now for the Parkhead side and played a key part in turning this game in Celtic’s favour as the minutes ticked away.

It was a pristine first touch from Weah after a long Scott Brown ball towards him that teed up the opening goal with Forrest sliding in front of Scott Tanser to convert at the back post and puncture the growing belief St Johnstone has had of sneaking something from the game.

By the time the game was out Weah had added a second after a fluid and speedy breakaway from Celtic with Scott Sinclair starting the move and Callum McGregor – who had ran from his own six-yard box - delivering an impeccable ball for Weah to convert.

The American’s enthusiastic celebrations would have struck a chord with the Celtic support but the manner of the jubilation that followed showed just how hard the Parkhead side had had to work for their openings.

Toljan almost made an immediate impact, too, on his debut for the club when he picked out Oliver Burke in the box only for the striker’s effort to be repelled by St Johnstone goalkeeper Zander Clark.

But the 24-year-old’s arrival coupled with the fact that Lustig is toiling now with an achilles problem perhaps points to the beginning of the changing of the guard at the right-back berth.

While Weah stole much of the headlines yesterday, the game started and ended with Ajer at its forefront. The Norwegian teenager required medical treatment just seconds into the game when he battered his chin off of the top of Tony Watt’s head in an aerial challenge.

There is a feeling that might not have hurt quite as much as his red card for hauling back Saints sub Callum Hendry. Ajer cut a forlorn figure as he headed up the tunnel without so much as a look in the direction of Rodgers with Celtic now facing Hibs on Wednesday with some scrambling around to be done.

And while the Parkhead side were largely in control of the game against St Johnstone, there were flashes of vulnerability that the Perthshire side did not quite make the most of.

In the opening five minutes St Johnstone had two decent chances to take the lead with Matty Kennedy able to ghost his way through the Celtic defence before whacking his effort off the legs of the advancing Scott Bain. As the rebound fell to Tony Watt, the former Celtic striker screwed a tame effort well wide of the target. Watt would later scorn a chance at the back post in the second period with the game still goalless that invited a furious response from his manager.

In a weekend that was dominated by penalty inquests, there was a feeling that there would be microscopic attention paid to any spot-kick calls. There were two; one when Burke went down in the opening period. Danny Swanson’s slack passback had been pounced on by the on-loan forward but as he headed through on goal he was brought down by Jason Kerr, with the Saints defender nicking a touch on the ball before taking out the striker.

There was more in the second period when both Ryan Christie and Edouard were crocked, but Rodgers wasn’t of the mind to offer a complaint at the calls.

“It was definitely a day for penalties, or supposed penalties,” said Rodgers. “I was just so happy to play well and win.

“It would have been harsh [Shaughnessy on Edouard]. The defender is trying to protect his goal. It’s last ditch, he is stretching. He got the ball and then made the contact. If that was a penalty given against me, I probably wouldn’t be so happy. It was just unfortunate for us. Shaughnessy has shown his bravery to stop it. Maybe on another day it could have been.”