Neil Lennon hopes fit-again Leigh Griffiths' best years at Celtic are still to come.
The Scotland striker came off the bench in the second half of the 4-0 Ladbrokes Premiership win over Livingston at Parkhead on Saturday for his first appearance since August due to personal problems, illness and injury.
In an interview with Celtic TV, boss Lennon encouraged the 29-year-old "natural born goalscorer", who signed from Wolves in January 2014, to keep on top of his fitness and go from strength to strength at the club.
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"I have spoken to him about this," said the former Celtic captain and midfielder, who also hopes the shoulder injury Jonny Hayes picked up against Livi is not as bad as first feared.
"I hope so. I didn't come to Celtic until I was 29 and people thought I had been here all my life.
"If you look after yourself and keep yourself in good condition, you can play for a long time now, the way the modern game is going.
"He certainly has the appetite for it. There is a hunger there to get back in and he really missed playing.
"Hopefully he will get fitter and stronger and have a good run of games now. He needs to do extra work, he needs to stay on top of his condition.
"He is in reasonable condition now and he is working hard and to make sure he stays fit.
"The fitter you are, the more robust you become and then you are less likely to pick up soft tissue injuries which is one that he had with a thigh strain.
"It is good to have him back, it adds that little bit of quality to the attack and strength that we already have."
Hayes injured his shoulder in the opening minutes but stayed on until early in the second half before being replaced by Greg Taylor.
Lennon said: "He is having a scan this evening.
"We are hoping it is just a muscle injury and if that is the case he should be good to go in the next week or so.
"We have a couple coming back. Mikey Johnston is back in training, we are hoping Mohamed Elyounoussi will be training by the end of the week.
"So fingers crossed Jonny isn't as bad as we first feared."