Djokovic, who lives in Monaco and lost to eight-times champion Rafa Nadal in last year's final at the first big claycourt event of the season, sprained his ankle playing for Serbia in the Davis Cup last weekend.
He has practised for the last two days but has not fully recovered.
"I can't still 100 per cent guarantee that I'll be on the court on Wednesday," the top-seeded Djokovic told a news conference on Sunday.
"I'll decide on Tuesday, at least to give time to another player just in case I don't play," he added.
"Strenghthening my ankle is still in the process. Things are looking good, better than I expected it to be.
"But I have to be realistic and cautious and see on some practices in the next few days, when I push myself to the limits, if I'm going to have any discomfort. It'll be an indication that I should not play."
Twice runner-up to Nadal at the glamourous event by the Mediterranean, Djokovic said he would not take any risks.
"Let's be honest, it's a very strong tournament and I think there's no room for any compromise," he said.
"It's a new surface, a new start of the season and, in order to compete on such a high level, I need to be 100 percent, no question about it."
But he realises that his special relationship with the tiny principality could help overcome his physical problems.
The Serbian proved it last season when he battled to the final although he was emotionally exhausted following the death of his grandfather during the tournament's early stages.
"I'm always feeling very inspired and motivated to perform my best in this tournament because I live in Monaco and I spend the majority of my time, when I'm not in tournaments, here in this club, practising on these courts," Djokovic said.
"There's extra motivation and inspiration for me to try to be fit and ready to perform," he added.
Djokovic, who won his third consecutive Australian Open title in January, said the injury would not prevent him from playing in the next claycourt events.
A six-times grand slam champion, the 25-year-old Djokovic is bidding to complete his collection with a French Open title, the only major trophy he has not won.
"I'm more than sure that there's not any danger for what's coming up next - Madrid, Rome and Roland Garros," he said.
Briton Andy Murray is confident he is fitter than last year, when he struggled with back problems and was knocked out in the quarter-finals by Czech Tomas Berdych.
"I'm in better shape. My back's not an issue like it was, so I feel better than I did coming to Monte Carlo last year," said second seed Murray.
The Scot, who was close to pulling out of the tournament before reaching the semi-finals of last year's French Open, said he had learnt to deal with the demanding tour schedule.
"Rafa has problem with his knees, Roger (Federer) has problem with his back ... I've been playing tennis for a long time, you pick up things. You have to manage your body," he said.
"You have to make sure it's a not a problem during matches. The back's not been doing this since the grasscourt season last year, so I'm not worried about that," added Murray.
"It's the movement that's been the thing I needed to improve on the clay and I feel like I'm moving better this year," he said.
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