Defending champions Paris Saint-Germain began their French Ligue 1 title defence without a host of stars as they lost 1-0 at promoted Lens on Thursday.
Striker Ignatius Ganago finished powerfully in the 57th minute after third-choice PSG goalkeeper Marcin Bulka passed the ball to him instead of teammate Marco Verratti, who perhaps should not have demanded it on the edge of the penalty area.
PSG were missing Kylian Mbappe, Neymar and five others who also tested positive for the coronavirus recently, including winger Angel Di Maria.
Six tested positive after a club-approved trip to Ibiza soon after their 1-0 loss to Bayern Munich in the Champions League final on August 23.
Mbappe was not with them and his positive COVID-19 test occurred while on international duty with France last week.
In their absence, coach Thomas Tuchel handed debuts to 18-year-olds Kays Ruiz-Atil and Arnaud Kalimuendo in attack, while the 20-year-old Bulka made just his second appearance.
He wasn't helped when Verratti sprinted to demand the ball and the flustered goalkeeper instead directed it straight to Ganago.
The Cameroonian brushed off Verratti's attempt at a tackle and smacked the ball into the top corner.
"Yes it was a bit dangerous but that's my way of playing. I always look for the ball because I play football. I asked for the ball," Verratti told broadcaster Canal Plus.
Earlier, Ganago hit the post after a fine run and shot in the 17th.
Lens should have made it 2-0 midway through the second half, but forward Simon Banza fluffed a close-range header.
PSG had long spells on the ball but hardly threatened.
"We struggled to create chances. We were missing players," Tuchel said.
PSG are at home against Marseille on Sunday followed by the visit of Metz to the Parc des Princes on Wednesday.