Scott Brown has not ruled himself out of Celtic's Europa League Group I opener against Atletico Madrid in Spain on Thursday.
The Scotland midfielder has missed the last game for both his club and country with an ankle injury.
"I'm getting very close to being fit," said Brown, who manager Neil Lennon wants to protect ahead of Sunday's Old Firm derby against Rangers.
"I'm touch and go for Thursday but I'll be fine for Sunday."
Lennon has vowed not to risk Brown in Europe if it makes him a doubt for the visit to Ibrox, but his captain still wants to play in both games.
"I did it in the Scotland game a few weeks ago and I've been playing with a tender ankle for the last couple of weeks and it has maybe just got the better of me the last few days," he said.
"I'm desperate to get back in on Thursday.
"I will try training tomorrow or Wednesday and take it from there."
Celtic's trip to Madrid is dependent on Uefa throwing out Sion's appeal on Tuesday against their Europa League expulsion.
Uefa's appeals committee will begin hearing the Swiss club's appeal at 0900 GMT and a decision is expected by the afternoon.
Sion had defeated Celtic in their play-off but were adjudged to have played ineligible players.
Brown missed Saturday's 4-0 win over Motherwell, after which Lennon said: "It's one where he needs rest, but with the fixtures it is difficult to give him that rest.
"He is such a good player and a valuable player for us, I don't like leaving him out at any time."
Brown's absence was scarcely felt as Motherwell were swept aside at Celtic Park, but a sterner test awaits in the Europa League group opener in Spain on Thursday night.
"Away from home in Europe, he is the type of player that I would want in the team," said Lennon.
"We won't have the lion's share of possession and won't create as many chances as we did against Motherwell.
"We are hoping he will get through the two games, but I will have to be advised by the medical team on that and obviously Scott himself.
"If I could choose, it would probably be Sunday for the league as the priority, but it would be a bonus if we had him for both games."
Explaining Brown's problem, Lennon said: "He tweaked it a little bit on Thursday and it was too sore to even train on Friday.
"It's not like Scott to be like that. If he pulls out of training, he must be in a bit of pain.
"So we will see how he is on Tuesday and hopefully he will be okay for Thursday."
Atletico have yet to score this season, went down 1-0 away to Valencia on Saturday and have just one point from their opening two games.
However, they have a virtually full squad to choose from for Thursday's match, including their £35m summer signing from Porto, Radamel Falcao.