Paris Saint-Germain need Kylian Mbappe fit and firing for Champions League semi-final against Manchester City

Striker's goalscoring prowess is key to Pochettino's side overturning 2-1 deficit in second leg on Tuesday

Kevin De Bruyne, with typical candour, had told a pre-match press conference he was not too familiar with the teenager tipped to line-up against his Manchester City.

At that stage, the tyro was not widely known. This was to be his first start in the Champions League and City were the clear favourites in their last-16 tie with upstart Monaco.

It was early 2017, and Kylian Mbappe had only recently turned 18. He grew up a great deal that night at the Etihad, and it made him famous.

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There were eight goals in the 90 minutes, Mbappe scored his first in Europe and it put Monaco 2-1 at half-time. Final score: 5-3 to City. By the end of the second leg, Mbappe had his second Champions League goal and City had been eliminated, on an aggregate score that read more like it should belong at the Monte Carlo Open, 6-6, with Monaco through on the tie-breaker of away goals.

Mbappe was picked for the senior France squad for the first time immediately after that breakthrough tie against City. He propelled Monaco to the French league title and, that summer, became the most expensive teen in the history of sport when Paris Saint-Germain signed him, on a binding loan deal, initially, to ease the budgetary impact of buying Neymar in the same transfer window.

On Tuesday, 22-year-old Mbappe will be back at the Etihad, and, once again, there is an element of gamble in whether or not to include him in the starting XI. He has been troubled by a calf problem since PSG's 2-1 defeat to City in the first leg of the semi-final that will be concluded in Manchester. He missed Saturday's 2-1 victory over Lens.

It might be reported, too, that Mbappe has recently suffered a Ruben Dias and a Kyle Walker problem.

It is a rare feat for any defence to shackle the explosive, in-form Frenchman, and among the startling statistics from City’s comeback from a goal down in Paris last Wednesday was the number of Mbappe shots on target: PSG’s leading goalscorer for the season – 37 across competitions – registered none, Dias his expert guard much of the time, Walker his equal in the sprint.

Defend that effectively on Tuesday and City will be on their way to a first Champions League final, while PSG, who reached their debut final in the competition last August, would anticipate some serious turbulence when they arrive home.

Gallery: PSG 2 Lens 1

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Neymar celebrates after scoring Paris Saint-Germain's first goal in their 2-1 Ligue 1 win over Lens at the Parc des Princes on Saturday, May 1. AP

In December they sacked Thomas Tuchel, who could tomorrow guide Chelsea into the final, and replaced him with Mauricio Pochettino, who will be judged very squarely on what happens Tuesday evening and over the next two weeks.

After the City game, Pochettino, Neymar, Mbappe and the rest of mainland Europe’s most expensively assembled squad will have three league fixtures to try to erode the stubborn one point lead Lille hold over them in France’s top division.

Lille's victory at the Parc des Princes last month meant they leapfrogged the serial champions – PSG have won seven of the last eight French championships – and they still cling to that advantage. With nine points to play for, the title is not in PSG's hands.

The defence of the French Cup is, and PSG will meet Montpellier in the semi-final in a week’s time. But if Pochettino ends up with just one major trophy – or less – by the end of May, the first sixth months of the year-and-a-half contract he signed in January will be deemed an unsatisfactory probation.

It is not likely to cost him the job, but it may bring with it a vexing summer, one where transfer targets are harder to persuade that PSG are likely Champions League winners in the near future, and where Mbappe’s own commitment is clouded.

The player has spoken openly about a desire to play for a club outside France at some stage in his career. His PSG contract expires in 2022.

Pochettino has backed himself to stimulate Mbappe’s loyalty to PSG, though his immediate concern is the limp his star striker was walking with as he boarded the squad’s flight to England yesterday. “We will assess him,” said Pochettino of Mbappe’s readiness to start against City.

Pochettino praised his team’s “character and resilience,” and said that, in the first leg, he had seen “perhaps the best 45 minutes PSG have played since I came in, but in the second half, we weren’t able to keep the same intensity and level.”

Pochettino has every reason to believe in a strong, compelling away leg. In the previous rounds, PSG scored four times at Barcelona, and three times at Bayern. The catch is that five of those seven goals were Mbappe's.