Stan Wawrinka won the Monte Carlo Masters in 2014Three-time Grand Slam champion Stan Wawrinka lost in the first round of the Monte Carlo Masters as he made his return to Tour-level tennis after 13 months out.
Kazakhstan's world number 36 Alexander Bublik beat the Swiss 3-6 7-5 6-2.
Wawrinka, 37, suffered a foot injury in early 2021 and had two operations.
He returned to competition at a Challenger Tour tournament in Marbella in March, where he was also eliminated in the first round.
"I think the body's getting much better," said Wawrinka. "I'm still far away from where I want to be, but I think I'm [going in] the right direction. I think today was a positive match. It was a tough loss, of course, but I'm happy with the way I was playing today."
Bublik said: "The only thing I can say is to wish Stan a speedy recovery, because if he would have been in shape, I wouldn't be standing here."
Elsewhere, Jo-Wilfried Tsonga's final appearance in Monte Carlo ended in defeat after he was beaten 6-2 6-2 by Croatia's Marin Cilic.
The Frenchman, 36, is to retire after the French Open, which starts next month.
Italy's ninth seed Jannik Sinner beat Croatia's Borna Coric 6-3 2-6 6-3, while Poland's Hubert Hurkacz breezed past Hugo Dellien of Bolivia 7-5 6-4.
Among Monday's other results, Fabio Fognini - who won the Monte Carlo title in 2019 - beat Arthur Rinderknech 7-5 4-6 6-3.
World number one Novak Djokovic opens his clay campaign on Tuesday when he plays Spain's Alejandro Davidovich Fokina in the second round.
