Neil Lennon will tell his Celtic players they might never have a better chance of making it to the last 16 of the Champions League before tonight's game against Spartak Moscow at Parkhead.

Celtic will qualify for the knockout stage for the first time since 2008 if they take more points from their match than Benfica do against Barcelona at Camp Nou.

Barcelona have already won Group G and are favourites to take three more points, but it was a worry for Celtic that the squad they announced yesterday did not contain Xavi, Andres Iniesta, Pedro, Jordi Alba, Cesc Fabregas or Javier Mascherano.

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That may be hugely encouraging for Benfica, although they will still have to contend with Lionel Messi.

Benfica are second in the group and Celtic third, with equal points and goal difference, but the Portuguese will go through on a superior head-to-head record between them unless Lennon's team take more points tonight.

A full house of 60,000 at Parkhead will hope to see their side go through. If they fail, the club will drop into the Europa League in the new year.

"I think they've got to go for it," said Lennon. "This is their moment and they might not get this opportunity again. I'm not going to put any extra pressure on them – I just want them to go and play as they can at home on a big European night: aggressively and with a good tempo to the game.

"We have players who can score goals, and have flair players who can rise to the occasion. They are capable of doing it."

Celtic's campaign has included the milestone of winning an away group game, against Spartak in Russia in October, and the astonishing home victory over Barcelona last month. A third triumph, the most significant of all, awaits Lennon if qualification can be secured tonight.

"In terms of achievement it would be as good as anything I've done. It's funny, because it hasn't really had the same sort of build-up of a huge game, certainly not the same kind of hype which surrounded the Barcelona game, even though there is more importance on this one. It would be the best achievement I've had as a manager," Lennon said.

"I just have to try and make sure we win our game. If Benfica win in Barcelona, so be it. We would have to congratulate them on doing that. That would be a magnificent effort from their point of view. We have to make them win, so the onus is on us to win at home.

"It will be difficult, it will be tense. We are playing a team who are coming here with nothing to really play for but their pride. They are very dangerous coming forward, but they do concede goals so it is there for us. We have more to play for. I think we need it more than Spartak do and sometimes that can take you a long way. But no games in the Champions League are a formality, especially when there is something riding on them."

Victor Wanyama is suspended and James Forrest, Paddy McCourt and Anthony Stokes are injured. A calf injury may prevent Aiden McGeady from appearing at Parkhead for the first time since joining Spartak in a £9.5 million deal in 2010, although Lennon acknowledged the possibility of the winger playing and doing damage to his former club.

"It wouldn't be a case of haunting us because, listen, we didn't show Aiden the door. He was a brilliant player for us and a great servant to the club. He wanted to go, the club felt it was the right time for him to go. We sold him to a good club where he has progressed. It was a win-win situation for everyone. So there is always that quirk in football where your ex-player comes back and bites you. But Aiden has a job to do and so do we."

The Celtic captain, Scott Brown, said finishing third and dropping into the Europa League would feel like an anticlimax after being so close to continuing in the elite competition. Celtic are on seven points and would become the first Scottish club ever to reach 10 in the group stages if they win tonight.

"Everyone [initially] expected us to finish bottom of this group," said Brown. "Finishing in third place would be a disappointment because we have had two closing games to try and do it. It's going to be really edgy.

"Everyone is going to want to know what's happening over in Barcelona. Fans will be listening to the radios and looking at their phones so I'm sure they will let us know."

Brown also said he had been free from pain for almost a month and was hopeful that a programme of rest, massages and treatment – rather than surgery – could allow him to continue playing despite his degenerative hip condition.