Derk Boerrigter has already indicated to media in Holland that he doubts if he will have recovered from his ankle injury in time to line up against his former club when they come to Glasgow for this first of these crunch games on Tuesday.
But sure to be standing firm against the Dutch champions is another key player from the Netherlands, Virgil van Dijk, whose impact since arriving from Groningen in the summer has catapulted him to a position where he is considered Lennon's best recruit of 2013.
However, as well as he has started, particularly in Champions League matches against AC Milan and Barcelona, and with Steven Mouyokolo sidelined for several months through injury, van Dijk refuses to rest on his laurels.
The 22-year-old still believes he must prove himself every time he takes to the field, at Lennoxtown or Parkhead, to ensure he retains his position at the heart of the defence.
He knows the challenge that exists from the likes of Efe Ambrose, Mikael Lustig and Charlie Mulgrew.
And, as he prepared to get back into action after a break while most of the first-team were away on international duty, van Dijk said: "We have much quality in the team and there are a lot of players who can play in my position.
"So I have to be sharp in training and in every game. I have to show I am number one for that position."
The partnership formed with Ambrose has improved on a weekly basis, the pacey and composed Dutchman bringing a stability to the Nigerian's often-erratic form.
Van Dijk believes it can only get better with games and time and said: "On the pitch, we understand each other. We sense each other and we know what we're going to do.
"If one of us makes a mistake, the other can make it right for them. We have a good bond and it feels good so far, so I am happy with that.
"We talked a lot about playing together, and, now that we do, it is going well and we want to keep it that way. It has happened quickly, but it is a positive thing."
Both players are comfortable bringing the ball out from the back, a tenet of the style manager Neil Lennon would like to see his side adopt, especially in Europe, where lumping it long is playing the lottery with all-important possession.
At times, it can leave fans -and team-mates - with their heart in their mouth.
But van Dijk looks unfazed as he heads upfield, often extending his mazy runs all the way to the opposition penalty area where he likes to have a shot at goal.
Not since the days of captain Roy Aitken has any Celtic defender so willingly joined the attack, reviving memories of cries of 'Feed the Bear' ringing round the ground when a goal was required.
Against Morton in the ill-fated League Cup tie last month, Lennon threw van Dijk up front for the closing minutes as they desperately searched for an equaliser.
It's not quite Total Football, but Van Dijk explained that, while he initially caught the eye of the Celtic scouts playing at the back, he is no stranger to operating in all areas.
"I originally started my career at right-back or centre- half," he told the Celtic View. "I never went up front, but I love to drive forward. Efe and I both enjoy doing that so that we can create things for the other players in the team.
"Everyone likes to join in with the attacking part of football. Every game I have a chance, but there is still no goal. I hope it comes soon.
"I know I can make a difference with my headers. But, unfortunately, it wasn't enough when I did it before (against Morton)."
If van Dijk can get off the mark against Hibs on Saturday, or even against Ajax next midweek, he will be delighted.
Retaining their unbeaten league record ahead of the third Group H match is demanded by Lennon who recognises how much improved his side has become at focusing on games before and after Champions League ties.
Van Dijk has already been visited by journalists from his home country seeking his views on the upcoming ties which could determine which club remains in Europe beyond Christmas, and which finishes bottom of the section.
He said of Ajax: "They are a very good team. They have lost two very good players (Christian Eriksen and Toby Alderweireld), but are a tricky side who like to keep the ball and create a lot of chances. We will have to work hard and put them under pressure."
Van Dijk studied Ajax's home draw with AC Milan on matchday two, and knows they'll feel disappointed they were denied all three points after a dubious penalty was awarded late in the match.
Celtic are still looking to get off the mark, and need to win on Tuesday to start rebuilding their proud home record.
But van Dijk isn't rattled and said: "If you look at the games we've already played, we had enough chances and deserved to get points from them. Unfortunately, it wasn't enough, but we have to stay strong.
"There are still enough chances to qualify from this group and into the knockout stages. But we have to get points out of the Ajax games.
"They will see Celtic as a challenge. They won't see us as the team at the bottom.
"They will have seen how we played against Milan and Barcelona and will know we can compete against them, too."