The 22-time Grand Slam title winner, back on court this week after three months on the sidelines, battled well but eventually crumbled against the hard-working world number 11 from Australia.
The 22-time Grand Slam champion had not played a competitive match since January but eased past the 62nd-ranked Cobolli in 85 minutes to reach the second round.
The 12th-ranked Greek, who will return to top 10 on Monday, also won the title in the principality in 2021 and 2022.
"First training... with the hope of being here these days before the start of the tournament. I'm here to see how it goes... with the desire to try to play," wrote Nadal on social media, alongside a picture of the Spaniard sitting courtside with his rackets.
Rafa Nadal's withdrawal from the Monte Carlo Masters has cast doubt over the 22-times Grand Slam champion's participation at the French Open, but Novak Djokovic said he is still hoping for a final chapter in their storied rivalry.
"Unfortunately I have to tell you that I am not going to be playing in Monte Carlo. My body simply won't allow me," said the battle-weary Spaniard on social media.
Jannik Sinner said he is enjoying every moment of his sensational start to the 2024 season after winning the Miami Open on Sunday for his third title of the year.
Novak Djokovic and Goran Ivanisevic are to go their separate ways, the tennis world number one announced on Wednesday, ending a five-year association which yielded 12 Grand Slams.
The emotion of the game itself, a missed chance for a third straight win in a tournament for the first time in over a year, was enhanced by Murray knowing this week was his final appearance in a city he calls his "tennis home".
Konstantin Koltsov, the Belarusian former pro ice hockey player and boyfriend of tennis player Aryna Sabalenka, has died at the age of 42, Russian club Salavat Yulaev said in a statement on Tuesday.
The Spaniard, still only 20, had not won a title since clinching his second major crown at last year's Wimbledon until he beat Daniil Medvedev 7-6(5) 6-1 on Sunday in a rematch of last year's final.
Zendaya and boyfriend and fellow actor Tom Holland were among the crowd Sunday as Poland's Swiatek beat Maria Sakkari 6-4, 6-0 to win the prestigious Indian Wells WTA title for the second time.
The victory ended Sinner's 19-match winning streak, including a 16-0 start to the year, and insures Alcaraz will remain No. 2 in the world rankings next week.
World number one Djokovic, who had not played since losing an Australian Open semi-final to Jannik Sinner on January 26, is chasing a sixth title at the desert venue in the season's first Masters event.
The Spanish icon's bombshell decision came four days after the 37-year-old lost a Las Vegas exhibition to compatriot and world number two Carlos Alcaraz.
"It's a good thing that as a player I will not face him many times," said Nadal, who expects to retire in 2024 after a series of injuries limited his appearances on the circuit.
IUB Presents 1st Bangladesh Female Squash Tournament 2024 was held on February 28 and 29 at the brand-new squash court at Independent University, Bangladesh (IUB).
Daniil Medvedev returned to action for the first time since his Australian final defeat on Tuesday with a straight sets win over Alexander Shevchenko in Dubai.
Andy Murray suffered another setback with a marathon loss to Czech teenager Jakub Mensik in the Qatar Open second round on Wednesday.