The Parkhead club have had no joy in persuading the duo to sign new deals, an issue which increases in importance each day the January transfer window looms closer.
Ahead of the Scottish Premiership clash with Hearts at Parkhead on Saturday, the Hoops boss was asked if, given the hold-up, he felt he was more likely to lose the Wales midfielder and Greece forward than keep them.
The Northern Irishman, who revealed defender Mikael Lustig faces four months on the sidelines after undergoing a double-hip operation, replied: "The honest answer would be, realistically, yes. The contracts are up in the summer.
"We are getting to the point where there will be a lot of speculation about both players but we have made it clear that we are willing to speak to them and we have spoken to Joe already but we have had nothing back.
"(They are) two players that we don't want to go but we can't force them to stay although we are doing everything we can at the minute to do that.
"But we have had no indication of what the players want to do.
"The ball is very much in their court at the minute.
"We are planning for next season anyway but obviously we would like some indication of what they are going to do. It is a difficult situation for us and for them.
"I spoke to them both personally a while back but I have had nothing back since.
"I have no idea if there are any offers for them, any interest in them. We have had no phone calls for them."
Lennon knows for certain that he will have to do without one of his best performers this season in Lustig.
The former Celtic skipper revealed the Sweden right-back had been playing through the pain barrier for several months.
With his country failing to reach the World Cup finals and Celtic out of the Champions League, the decision was taken to undergo surgery.
Lennon said: ''Lustig had surgery, four months. He had both hips done, so the procedure was a bit more in-depth than first thought.
"We are hoping he will be back March/April time but he had a lot of work done which makes his recent performances even more remarkable.
"His movement was restricted and he was in a lot of pain after games so it needed doing. So hopefully he will come back an even better player which will be brilliant for us.''
One player who could bolster Lennon's squad is Japan midfielder Hiroki Yamada who has been on trial at Lennoxtown this week.
The Celtic manager admits it is possible that the player, who plays in the J-League with Jubilo Iwata, could be offered a deal.
"He's done okay," revealed Lennon. "He will be here for another day or two. So we will run rule over him.
"He seems to have adapted okay."
Celtic beat Hearts 7-0 when they met in the Scottish Cup at Tynecastle at the start of the month but Lennon admits it will be hard for his players to reach the Utopian standards he believes they attained in Gorgie that day.
"It is very difficult to do that, it is a different competition and we are at home," he said. "The onus is on us to take it to Hearts.
"Hearts will have their own agenda in terms of being hard to beat. We have to find a way of breaking them down and I am positive that we will.
"It is not nice when you are on the end of a beating like that as you know and it is important that you get a reaction and (manager) Gary (Locke) will be looking at that.
"I remember we beat St Mirren 7-0 and then lost to them in the cup the following week so no two games are the same.
"So we have to try to maintain our level of performances which has been very good domestically."