Only two weeks after falling short of victory despite a record-breaking hat-trick in the World Cup final, French sensation Kylian Mbappe returned to action with Paris Saint-Germain (PSG), looking to get over his Qatar heartache with an early comeback. However, things did not turn out to be any different with club football as the 24-year-old, the Golden Boot winner in last month's showpiece event, found himself on the losing side again.

Facing a water-tight defensive line, Mbappe struggled to make an impact as PSG suffered their first league loss of the season after being stunned 3-1 by Lens on New Year's Day. With Argentina's World Cup-winning captain Lionel Messi being given an extended break and Neymar suspended after receiving a red card against Strasbourg, PSG needed their only remaining world-class striker to deliver.

However, Mbappe was kept uncharacteristically quiet throughout the game, and PSG's fragility against fluid counterattack was ruthlessly exposed by an intrepid Lens side. The hosts led after five minutes when Przemyslaw Frankowski fired home from close range. Hugo Ekitike quickly equalized for PSG after finishing from a tight angle, but Lens restored their lead just before the half-hour mark when Lois Openda found the back of the net.

The lively Openda, who utterly overshadowed Mbappe, repeatedly terrorized PSG defenders with his ingenious dribbles and duly punished the French giants again in the second half as the Belgian youngster brilliantly back-heeled the ball into the path of Alexis Claude-Maurice, who comfortably sealed the win.

"I struggled to recognize my team. We lacked solidarity and we got wiped out the more the game went on, leaving them far too much room," observed PSG coach Christophe Galtier afterwards. "In fact, we did the opposite of what we should have. We struggled against Lens' pressing, we should have played more long passes to make them defend deeper."

PSG captain Marquinhos shared the somber mood, admitting that the absence of Messi and Neymar cost them dearly. "They are two great players who make the difference but that is not an excuse," he told a press briefing. "We lacked cohesion, efficiency and intensity."

When asked about Messi's extended holiday, Galtier said, "Leo had a brilliant tournament, given they won the competition, he went back to Argentina for the celebrations. We made the decision to give him until January 1, so he will be back here with us on the second or third to get back into the swing of things after 13 or 14 days off."

"There are individual cases with the players who went very far," Galtier added. "Achraf Hakimi played in every game at the World Cup for Morocco. He was in the team of the World Cup. He wanted to get back as quickly as possible, as did Kylian Mbappe.

"He also turned in some brilliant performances and was the top goalscorer at the World Cup. After speaking to him and all my different teams who stayed in regular contact with the players, Mbappe wanted to join back up with us pretty quickly.

"There could be a time when Hakimi and Mbappe need to rest. Not necessarily physically, but definitely mentally."

Mbappe could be forgiven for feeling physically and mentally exhausted. Earlier this season, he indicated that he was not given the status he wants on and off the pitch despite rejecting Real Madrid's offer to stay in Paris. The wunderkind, who was the undisputed talisman in France's attempts to win back-to-back World Cups, hasn't been pleased with the role he's been forced to play at PSG to assist Messi and Neymar.

But when Mbappe was granted the chance to step out of the South American duo's shadow on Sunday, he failed to step up to the breach. As has been the case at the World Cup, Messi hogged the spotlight, and most of the questions during the post-match press conference were about the Argentinian maestro.

Messi is certainly extremely important to PSG despite his advanced age. The seven-time Ballon d'Or winner has netted 12 times and notched 14 assists in all competitions this season. But the overwhelming reliance on Messi's brilliance is a huge problem for the Ligue 1 behemoth. Sometimes, the pressure could be simply too much. Mbappe needs to raise his game, especially when the going gets tough for PSG.