Steve Clarke has warned Leigh Griffiths he will have to be in top shape if he wants the chance to fire Scotland to Euro 2020.

The national team boss has included the Celtic striker in his squad for the first time since taking over as reward for Griffiths’ recent return to scoring form.

A combination of injury and personal troubles have prevented the 30-year-old from adding to his 19 caps since his last appearance against Albania in September 2018.

His last goal for Scotland was against Slovenia 11 months before that but having seen Griffiths find the net against St Johnstone and Aberdeen over the past month, Clarke is convinced he could yet have a major say as his team look to sink Serbia in Belgrade on November 12 and book a place at next summer’s European Championships.

However, the Hampden boss has made it clear Griffiths will have to be at full fitness if he is to get his chance to become a national hero.

Hoops manager Neil Lennon was left fuming when the frontman returned to pre-season training overweight and admitted again after his recent Pittodrie strike he was still not fully up to speed.

Now Clarke has encouraged the striker to sharp up quickly.

“When you look at Leigh over the years he’s always been a goalscorer,” he said. “He’s a dangerous player in the 18-yard box.

“The goal he scored a couple of weeks ago at Aberdeen shows you what he’s all about really.

“Sometimes off the bench you need a goal and with Leigh in the squad he gives us that option.

“Lawrence Shankland gives us it too. The more options I’ve got the better and Leigh is certainly one of those options.

“I think he has to be 100 per cent when he goes to the pitch. Whether he goes to the pitch for 97 minutes, 120 minutes or 20 minutes, he has to be 100 per cent.

“Every player we’re looking to play, has to be at 100 percent for whatever amount of time they are on the pitch.”

Hearts goalkeeper Craig Gordon and Norwich defender Grant Hanley have also been welcomed back into a 27-man squad as Steve Clarke prepares for this month’s crucial triple-header, which also includes trips to Slovakia and Israel for the Scots’ final two Nations League fixtures.

Gordon was the Hampden hero for Hearts over the weekend as his man-of-the-match display against Hibernian helped earn the Jambos a place in next month’s William Hill Scottish Cup final.

Ryan Christie, Stuart Armstrong and Kieran Tierney – who all missed last month’s clashes with Israel, Slovakia and the Czech Republic – are back following a period of self-isolation, while defenders Scott McKenna and Liam Palmer return after shaking off the knocks which also ruled them out.

“It’s certainly the biggest squad we’ve had,” said Clarke. “With three away games I thought it would be better to put together a bigger squad.

“I’ve always liked Craig as a goalkeeper. I actually spoke to Craig last year when he was at Celtic about his situation and where he was.

“I just felt he was very positive about being involved in the national team again. I think he made a big decision in the summer to leave Celtic and go play at Hearts, so he’s put himself out there.

“Grant’s had a tough time of if with injury but plays week in, week out when he’s fit. He’s captain of Norwich and has plenty of international caps. Hopefully he stays fit and is a good addition in an area of the pitch where other players have done well recently.”

Clarke’s team will aim to finally end Scotland’s 22-year wait to reach a major finals when they take on the Serbs, while their Nations League clashes could also have a major bearing on the Tartan Army’s 2022 World Cup hopes.

Scotland currently top League B2 and need just one more win to all-but guarantee themselves the insurance policy of a play-off slot for the tournament in Qatar.

“It’s obviously very, very important that as a group we try to deliver what the Tartan Army want, which is to be in the finals of a major tournament again after a long, long wait,” said the manager.

“On the back of that we then have two really important games where we can win the League B section and gain promotion to the A group which would be great for the country and the co-efficient, and would help us in future qualifying campaigns.”