Brazilian star Neymar and his coach Thomas Tuchel fully agreed Tuesday that no-one at Paris Saint-Germain was "yet at 100 percent."

"I'm not at 100 percent of my fitness, no-one is at 100 percent, it's the start of the season and we haven't played many matches," said Neymar ahead of Wednesday's Champions League home game against Red Star Belgrade.

"World football reaches its peak around February and March, with the biggest matches.

"I'm working, every match, every day, on improving both physically and technically," Neymar added.

Asked about the foot injury in February which ended his PSG season and compounded his build-up to the World Cup in Russia, Neymar said it had made him "very sad."

Brazil's elimination from the quarter-finals of the competition was also a source of "great frustration".

But he added: "My injury, the World Cup, they are in the past."

Neymar has scored seven league goals already this season, including a brace in the 3-0 win at Nice at the weekend which saw PSG make it a record-equalling eight straight victories at the start of the French campaign.

However, they lost 3-2 at Liverpool in their Champions League Group C opener last month, making a win at home to Red Star vital ahead of a double-header against Napoli.

Tuchel said Tuesday his positive public statements after the loss at Anfield were not the same as his "unofficial" reaction.

"You can well imagine that the official reaction should not be the unofficial reaction," he said.

"It was a very tough defeat for us, we did not play to our best. Certain criticism had to be made in the dressing room.

"It was only the first match in the group, so you cannot exaggerate the criticism, we had to keep calm," said the German.

"I am very happy with their reaction, we have to continue tomorrow."

After saying that Neymar was not quite at his best, Tuchel added: "For me, it's normal because he was injured for a long time and it was a very difficult and complicated World Cup for him."

"He did not have a normal pre-season and everyone is watching him to see if he is in top form or if he makes mistakes, it's difficult for him.

"He's a player who needs to be in a good state of mind, training with a smile.

"Honestly, I am very happy with 'Ney', he will reach top form, 100 percent, and that is very necessary," the coach said.

"Now he is very confident, involved in the club and in the project here and we are very satisfied."

Red Star are in the group stage for the first time since 1991-92, the season after they won the European Cup by beating Marseille on penalties in the final.

They held Napoli to a 0-0 draw in their group opener but coach Vladan Milojevic is realistic about what lies in store for his side on Wednesday.

"There are no words to describe the team we will be facing," he said.

"I am proud to see where my team are, and we deserve it because we are the biggest team in the Balkans."

Police in Paris, meanwhile, are mostly concerned about ensuring there is no trouble.

Red Star fans were officially banned from travelling to the French capital following incidents at their game against Salzburg in the play-off round.

But there is a large Serbian community in the Paris region and more than 2,000 Red Star fans are expected at the Parc des Princes, mixed in with the home support.

"It would be good for PSG and for us if we could have the passion of our supporters without them creating anything else," said Milojevic.