Both players live and train in the posh European city.
Djokovic has seen some positive signs in Raonic's routine.
"He's a very disciplined player, always works out," Djokovic said. "Always spends a lot of time in the gym, off the court, preparing himself for tough battles."
If Raonic stands any chance of earning his first career win over the world's No. 1 player when they meet on Wednesday at 3:30 a.m. ET, the key may rest in his improved physical endurance and mental strength.
At the end of his five-set win over Feliciano Lopez, Raonic was still serving bullets at 220 km/h. And despite squandering 10 break points, he never seemed to get down on himself.
"The thing I've gotten better at is I haven't let it sort of linger in my mind," Raonic said of the missed chances. "I've been putting that behind me."
Ivan Ljubicic, Raonic's coach, says he's seen positive signs in his mental game.
"[Milos is] one of the most determined and motivated people that I have ever met, and that meets my needs and my type of people that I want to work with," Ljubicic said.
In the four matches he has played against Djokovic, Raonic has only won a single set. But Djokovic doesn't put too much stock in his past dominance.
"He's been playing some great tennis in the last 15 months," Djokovic said. "He deserves to be where he is now, top 10, coming closer to the top five in the world."
Raonic scored his only win over one of the "Big Three" — Djokovic, Rafael Nadal and Roger Federer — last year at the Paris Masters when he beat Federer.
If Raonic is to climb up the ATP rankings ladder and reach the top five, he'll need to pull off another upset against an all-time great.
And Djokovic isn't looking too vulnerable. He hasn't lost a set yet in the tournament.
After losing in the Australian Open quarter-finals last year, Djokovic has reached at least the semifinals of the French Open, Wimbledon and the U.S. Open.
Raonic, however, has his serve clicking, recording 99 aces so far.
Raonic vs. Djokovic head-to-head
Raonic and Djokovic have faced each other four times. Here's a breakdown of what happened:
2013 Davis Cup semifinal- Djokovic won 7-6, 6-2, 6-2. Raonic was dealing with an ankle injury and seemed to struggle on the clay.
2014 Rome Masters semifinal- Djokovic won 6-7, 7-6, 6-3. Raonic's serve gave Djokovic fits. "I can’t recall last time when I was feeling so helpless returning, even his second serves,” he told the Telegraph. Djokovic still won, because, well, he's Djokovic.
2014 French Open quarter-final- Djokovic won 7-5, 7-6, 6-4. "Djokovic brutally exposes Raonic's limitations," read the headline on the Roland Garros website, an apparent dig at the Canadian's over-reliance on his first serve. Djokovic handled the challenge without much stress.
2014 Paris Masters final- Djokovic won 6-2, 6-3. Coming off his first ever win against Roger Federer, Raonic may have been a bit winded for this one. "Every time he put his racket on the ball, he was making me play a deep ball," Raonic said after this match. His serve didn't put Djokovic on edge at all.