Leigh Griffiths signed a new contract with Celtic last week but the hard work is just beginning for the striker as Brendan Rodgers urged the player to knuckle down and give his football his full focus.

There are two ways to look at the contract extension offered to Griffiths; a measure of how important his goals are to the club or, a more cynical suggestion, is that the club preserve the selling value of a player who still has much to prove to his line manager in the wake of one high profile striking departure from the club this summer.

There is no little irony in the fact that Griffiths is the one player who would have felt confidently assured the minute Rodgers first walked through the front door at Celtic.

Cavorting with the league trophy that day in front of the 13,000 who had turned out to see Rodgers formally unveiled as Ronny Deila’ successor, Griffiths’ party mood was easy to explain on the back of a 40-goal season.

Moussa Dembele’s arrival, however, quickly changed the picture and there is a feeling that Griffiths has never quite been so surefooted around the first-team ever since.

There have been perennial whispers of a sloppy approach to training and of off-field distractions and certainly Rodgers has not been shy in explaining that there needs to be more to come from the Scotland internationalist.

Griffiths hit the 100-goal mark for Celtic last month but those two goals that took him to the century are his only return so far this term in 11 appearances while his frustration was compounded by falling down the pecking order with Scotland.

“With the big clubs you’re always going to be challenged,” said Rodgers. “You can never think you are the number one striker. No, you always have to think you’re being pushed and challenged.

“That’s the way it is.

“Big clubs will always have options, you always have to fight to prove yourself every day in training and in every game.

“And if you don’t, and you drop off a level, whatever your fitness or preparation, then there’s always someone else.

“But I think what he’s done, and what he’s shown, is that he’s the ability to score goals.

“What he has to keep doing is keep working, keep fighting, so those opportunities come. That he’s fit and ready to take them.

“I think he’s great to have in our squad, that’s why we wanted to give him another deal. He’s an important member of the squad. We know he can score goals. But, like I say, at top teams it’s about more than that.

“But it’s something he’ll continue to work hard on, that side of his game. That will always improve his chances domestically and, of course, also at international level.”

Griffiths was irked to find himself on the outside looking in for Scotland last Monday night when he was replaced by Steven Naismith for the game against Albania.

The striker insisted in the aftermath of the game that it was a “kick in the teeth” to have the Hearts striker jump ahead of him in the pecking order, but Rodgers has warned Griffiths that he needs to be prepared for the fact that he is not judged now on goals alone.

“I was at the Albania game and Naismith I thought was excellent,” said Rodgers. “He worked his socks off and got us two goals – you can’t complain with that.

“For every player, Leigh knows his qualities but he has to, at this stage of his career, now, to work tirelessly at all aspects of his game.

“The modern game now the strikers are changing. If you look at the evolution of strikers, it is not just about scoring goals any more, you have to do more than that.

“Strikers are now running underneath, pressing from behind, working, so there is no other way you can take that out other than on the training field and work even harder. When opportunities are there then you come and take them.”

And it is the day-to-day environment of putting on the boots and getting to work without an audience where Rodgers wants to see the real graft.

“I always explain this to players who want to be the very best they can be,” said Rodgers. “The first thing I ask them is ‘where are you at training?’ Because if you want to play like Coutinho or Suarez or these types of guys, you need to be eight, nine out of ten in training every day.

“Now, if you think you can work at a five or six out of ten, then you’re not even ready to train with these guys — never mind play with them.

“So you’ve got to get your training right here in order to have a chance.

“That’s the modern game at the very highest level, or the levels you try to aspire to.

“Training is so important, you need to be ready to work and then when opportunities come, whether you’re Leigh Griffiths or anyone else, you need to be ready to take them.

“That’s the message to every player, not just Leigh. You have to be ready to do that.

“Then you have a difficult job as a manager. Otherwise, if people aren’t pushing themselves then it’s quite an easy job.”

Griffiths and record summer signing Odsonne Edouard have netted six goals between them since the start of the campaign and Rodgers wants to see more from both players.

“We need to be much more clinical in the final third,” he said. “My trust in the players is 150%. Since I came here they have given us absolutely everything. They have been brilliant. But I think we need to be a little more dynamic in the final third of the pitch.

“We need more in the final third but that comes from everyone all the way through the team. You have got to get it quicker and into forward areas. When it gets forward, combining better and having better quality and being clinical.

“We have lost players who are goalscorers, first and foremost. But we still have enough here in the squad.”