Neil Lennon has more cause than most to fret about this week's international fixtures. A consequence of Celtic's multi-national squad is that, on occasions such as the coming days, a batch of players depart to represent their country. Already, Efe Ambrose is featuring for Nigeria at the African Cup of Nations.

For Lennon, the spectre of the Champions League last 16, first-leg match against Juventus on 12 February means he will view this particular schedule of fixtures with trepidation. It already seems certain that Celtic will field a shadow team for Saturday's trip to Inverness, aside from the goalkeeper Fraser Forster who again missed out at Raith Rovers because of a neck problem.

"Is it a worry to have so many players away on international duty? Yes," Lennon conceded. "Of all the weeks to have international games – I don't know who decides or puts these dates in place. We have got the biggest game in four or five years at the club coming and we have players all over the world.

"It's a concern. We've got at least seven or eight players away but I will make changes for Inverness next weekend. I'll keep the big boys thriving for the Juventus game."

Four of Celtic's squad – Kris Commons, James Forrest, Charlie Mulgrew and Scott Brown – are in Gordon Strachan's first Scotland party, for the meeting with Estonia in Aberdeen. "I have spoken to Gordon about the Scottish players and he understands my situation," Lennon added. "I have every trust in Gordon to deal with that properly.

"I haven't asked him not to play anyone. James could do with some game-time, Kris might need a wee run-out. Scott and Charlie have played all season. I'll leave that up to Gordon. I'm not going to pick his team for him."

There was, however, no cause for Celtic anxiety here as they eased into the quarter-finals of the Scottish Cup. Commons earned and scored the opening goal with a penalty, which was disputed by the penalised Simon Mensing. "He went down too easily and I know that for a fact," Mensing said. "I'm really disappointed with it. There was minimal contact but Commons is clever."

The visitors scored two late counter-atacking goals through Forrest and Mulgrew. Forrest's intervention was especially notable, on what marked his latest return from injury. "James is a wonderful talent," added Lennon. "One of the best Scottish players the country has produced for a long time.

"He's been training great and we've been desperate to get him in – but the physios have been holding him back. He got a few minutes today and we hope he will get some game-time with Scotland this week.

"We hope he will play at Inverness next week and we can get him ready for Juventus – which we have tried to do with the whole squad.

"Basically since after the winter break we have had this huge game looming on the horizon and we've tried to keep the squad healthy."

Man of the match Charlie Mulgrew (Celtic)