Talk might be cheap but it could be priceless for Celtic.

If Leigh Griffiths has taken the advice to do his talking on the pitch then there is no ignoring the shout that has come from the Scotland internationalist; three goals, three games.

Indeed, the striker can boast to scoring Celtic’s only three goals from their trio of recent outings.

There were just six minutes remaining of what had become yet another frustrating night for Brendan Rodgers’ side when Griffiths finally punctured the weight around the team with as he pounced to convert a block from Scott Tanser and finally breach a goal that Celtic had laid siege to for much of the second period of this game.

The sense of relief was difficult to ignore. On the back of a slipshod start to the season on which the club have stuttered their way through their opening sequence of games, ensuring they come through this game unscathed had taken on all sorts of importance.

They did it but it ought to have been significantly more comfortable than it was. The only real damage came with Dedryck Boyata’s late sending off for an apparent use of foul and abusive language to an official but the curses would have been far more visceral had Celtic not come through this game.

The League Cup was the first trophy Rodgers claimed as Celtic manager and this victory in Perth was his 20th Cup win with the Parkhead side. For the second successive game, Rodgers rang the changes with the call to go with both Odsonne Edouard and Griffiths a welcome one. Rodgers arrived at the club, the decision to go with two strikers was a welcome one.

Not that it made much real difference in a turgid opening 45 minutes. Celtic looked insipid for the bulk of the opening period, and it was difficult not to note that the two good chances they did create would have routinely been put away when they were playing with their tails up.

Instead the opportunities scored by Griffiths on the half hour mark and McGregor on the cusp of the half-time whistle seemed to accentuate the lack of confidence in the current side.

The first had come after a diagonal ball in from the left-hand side from Edouard landed perfectly on the head of the Scotland internationalist but his effort was tame and straight towards St Johnstone keeper Zander Clark.

Then McGregor dragged an effort wide of the target after a finely weighted ball from Ntcham. As Celtic toiled to break down St Johnstone and find openings in the Perthshire side, the Frenchman’s pass seemed certain to puncture the growing pressure within Celtic’s ranks.

Instead, McGregor collected and burst through but at the last minute pulled his shot just shy of the target.

In between times Celtic had been forced to rejig things when Kristoffer Ajer pulled up with what seemed like a hamstring strain, meaning that Jack Hendry was back into Celtic’s backline to replace the Norwegian.

The defender has become something of a weather vein for all of the Parkhead side’s ills but the malaise has affected more than just the backline of this Celtic side.

It was evident in an opening period in which St Johnstone camped themselves in their own half and invited Celtic to come at them. Devoid of any real penetration it was a struggle for Rodgers’ side to bore their way through and carve open Tommy Wright’s side.

McGregor brought out a save from Clark from the restart with an effort from the edge of the box and from the resultant corner Ntcham drew another stop from the keeper with an acrobatic attempt.

It seemed to revitalise Celtic somewhat with Dedryck Boyata heading just over the bar shortly afterwards as the visitors raised the tempo. Griffiths was next with an effort that seemed to be palmed beyond the goal by Clark, although no corner was forthcoming.

At the other end of the park Bain had to muddy his gloves when Blair Alston had an effort but the majority of the traffic was one way.

McGregor was back to harry Clark again with another long range effort that the St Johnstone keeper tipped over the bar.

With Celtic chapping at the door it seemed inevitable that a goal would come. However, a slip by Ntcham allowed Alston another sniff at goal albeit that his effort was well wide of the target.

It served as a reminder, however, of just how precarious the tie was.

Lewis Morgan took over from Edouard as Celtic looked for the breakthrough. The former St Mirren winger almost found it immediately when he made space for himself on the edge of the box but his effort was just over the bar.

The chance of the night, though, fell to Griffiths. Having scored in his last two successive games the odds would have been on the striker bursting the net after McGregor’s ball went over the top of Joe Shaughnessy but Clark throw out his leg to deny the forward.

As Celtic were bemoaning their luck it almost took a significant turn for the worse when David Wotherspoon unleashed a swirling effort that curled just wide of the top corner.

Next up was Tom Rogic as Celtic made their final change. By this stage St Johnstone were entrenched deep within their own box as Celtic came at them but the clear issue for the Parkhead side is finding a way to turn that dominance into a tangible scoreline. When it finally came, the relief was obvious. Kieran Tierney’s cross was met by the head of James Forrest whose effort was blocked by Tanser. Initial appeals for the use of a hand were ignored as Griffiths pounced to bury the ball low into St Johnstone’s net.