LEIGH GRIFFITHS says that Celtic will prove their critics wrong this season, and he has vowed that the best is yet to come after their opening day demolition of St Johnstone on Saturday,

The striker came on as a substitute and scored to round off a 7-0 thumping that Griffiths believes has sent out a marker to the rest of the Premiership as Celtic kicked off their tilt at a ninth consecutive title in fine style.

And with so many first-team players still to come back into the fold, Griffiths says that it won’t be long before Celtic’s detractors are eating their words.

"We let other people talk and say what they have to say,” Griffiths said.

"As players, we do our job on that on that pitch and you look at the performance against St Johnstone. If people think we are weaker when we are winning 7-0, how much better can we get?

"We look strong. We were missing Christopher Jullien, Jozo Simunovic and Kieran Tierney on Saturday. You also have the attacking players who weren't in the squad – (Tom) Rogic, (Marian) Shved and (Vakoun Issouf) Bayo.

"There are a lot of players who will come back and make us even stronger. It's up to the gaffer how he uses us - but that was a great start to the league season.

"We will probably be judged on Europe, but we couldn't have asked for a better game to go into Wednesday off the back of.

"Cluj are a good side but we will go there with confidence after a 7-0 win.”

Griffiths took another step towards full fitness on Saturday and looked sharp during his cameo in the game, setting up strike partner Odsonne Edouard for the sixth goal before bagging the seventh with a fine strike from the edge of the area.

He maintains that he is still some way from peak condition, but is delighted to see that his hard work is paying off.

"It's easy coming on in a game like that,” he said.

"The space had opened up, St Johnstone were getting tired and you saw the chances we created in the second half. It could have been more than seven in the end - but we'll take it.

"I feel about 70 to 80 per cent fit right now. I still have a bit to go. I am working with John Currie every day out on the training field.

"It's about doing my stuff out there and working in the gym. The quicker I do that, the quicker I will get to 100 per cent.”