Paris Saint-Germain's deepening Champions League woes have turned the focus back to the strength of competition -- or lack of it -- in the French top flight as they prepare to face bitter rivals Marseille this weekend.

On Wednesday, Neymar and Kylian Mbappe were shut out and PSG needed a brilliant injury-time goal from Angel di Maria to salvage a 2-2 draw at home to Napoli.

Thomas Tuchel's side now face a real fight just to qualify for the Champions League knockout rounds, having already been beaten at Liverpool.

After disappointing last-16 exits against Barcelona and Real Madrid in the last two seasons, Tuchel is tasked with finally making the Qatar-owned club a genuine contender in the Champions League. It is therefore galling for those in charge in the French capital to find themselves at risk of an early exit.

"I knew it was perhaps the most difficult group we have had in my time here," said midfielder Marco Verratti after Wednesday's game.

"Now we need to go and get a great result in Naples, and then everything will be decided at home against Liverpool. I still think we can qualify."

Tuchel admitted Paris have to improve, but weaknesses in his team were badly exposed by Napoli.

Yet at the same time PSG go to Marseille having won all 10 games in Ligue 1 this season, smashing the previous French record of eight straight victories at the start of a campaign, set by Olympique Lillois in 1936.

Another three points on Sunday and PSG will match Tottenham Hotspur's achievement of 11 successive wins at the start of the 1960-61 season, a record in Europe's big five leagues.

Tuchel's team are already eight points clear of Lille atop the table, and 11 points above Marseille in fourth. A sixth title in seven seasons seems inevitable even now.

That should not be a huge surprise, given that PSG's operating budget -- a reported 500 million euros ($568m) -- is almost double that of France's next richest club, Lyon.

When PSG played Lyon earlier this month, they won 5-0, and perhaps the lack of a proper challenger domestically removes some sharpness from their game in Europe.

Nobody said that of Monaco when they reached the semi-finals of the Champions League in 2017, of course. Nevertheless, the results of French teams in Europe this season have led to much soul-searching.

Europa League finalists last season, Marseille are already staring at an early exit from the competition after losing 3-1 to Lazio on Thursday, not ideal preparation for the meeting with PSG at the Velodrome.

Marseille, the only French team to have won the Champions League, despise the club from the capital, and the clash between the country's two biggest sides is a major event in France. However, seven years and 17 games have passed since Marseille last beat PSG.

Second-placed Lille host Caen on Saturday, while Thierry Henry makes his home debut as Monaco coach against Dijon.

The former Arsenal and France star lost 2-1 at Strasbourg in his first match in charge last weekend.

His depleted team then drew 1-1 with Club Brugge in Belgium in the Champions League, and Monaco have now gone 12 games without winning.

"I know every little corner of the stadium and lots of memories will come back," said Henry of returning to the Stade Louis II, where he began his playing career.

"I am not looking for excuses but starting with two matches away from home was not the best way to reassure ourselves.

"Monaco are not used to being in this situation. We have several players who played for struggling teams last season and we need their experience."