Thomas Tuchel admitted Paris Saint-Germain missed Neymar in their shock defeat to Rennes and ruled out an exit for the Brazil star unless an adequate replacement is brought in.
Neymar's prolonged absence from the PSG squad continued on Sunday as the Ligue 1 champions fell to a 2-1 loss at Rennes in their first away outing of the new campaign.
The 27-year-old Neymar has been recovering from an ankle injury that has ruled him out of action since early June, while questions remain over his future amid strong links with Real Madrid and former club Barcelona.
After seeing his side struggle for creativity at Roazhon Park, however, head coach Tuchel stood firm on his stance that PSG must keep hold of the player.
"He will not leave without recruitment, it is not possible," Tuchel said at his post-match news conference. "It's clear - if he stays, we will have a player who will help us win.
"We lacked capacity for acceleration. There were small situations where space opened but we were not decisive."
Tuchel told Canal +: "I always say the same thing, the transfer window is open even more than 10 days and you think it will be settled tomorrow or the day after tomorrow?
"What I think is not important. Today my player cannot play because he has not done any training like the others. This is the situation, and nothing has changed."
Edinson Cavani was gifted a 36th-minute goal by Rennes following an error from Damien Da Silva, but PSG managed just one further shot on target and were made to pay by the side that also beat them in April's Coupe de France final.
Goals either side of half-time from M'Baye Niang and Romain Del Castillo handed Rennes all three points, but Tuchel downplayed the magnitude of the defeat so early in the season.
"It was a difficult match, but we expected it," he said. "We do not have everyone available. Some players only participated in two weeks of training.
"These situations are normal in August. We are not at our best. Against a physical team like Rennes, who gives everything, whose players run like crazy, in a match in prime time, it's normal that it was complicated for us.
"We scored the first goal, we controlled the match and made mistakes. We had to close the match after the first goal. We were not able to do it.
"We conceded a goal with a two against one in the area. We got very close to the Rennes area, but we lacked tenacity to win against some offensive.
"In these conditions, it was difficult to create opportunities. We can lose a match like that, but we could win it too."
Despite a run of five away defeats in six league matches stretching into last season, Tuchel insisted he does not fear the sack and called for some patience.
"I'm a very happy man," he said. "There is no one who is putting more pressure on myself than me. It's the same for every coach."
"We can play better than today. Things are not easy - everyone has improved in Ligue 1 and the Champions League. It's time to be patient and to keep your confidence. We cannot question everything after a bad result."