LISBON, Portugal — Only time will tell how long Manchester United will be without Marcus Rashford, following the knee injury sustained by the forward moments after his decisive goal in the 1-0 Champions League victory over Benfica in Lisbon, but Jose Mourinho will be praying that it is a brief spell on the sideline.

Not for the first time in European competition, Rashford delivered when it mattered for United, and so did Mourinho, with his free-kick winner in the Estadio da Luz courtesy of a catastrophic error of judgement by 18-year-old goalkeeper Mile Svilar, who eclipsed Iker Casillas as the youngest ever to play in the Champions League.

Five months ago, Rashford scored another match-winning free kick in the Europa League semifinal first leg against Celta Vigo in Spain, and though his goal against Benfica might not have the same significance, it certainly spared Mourinho the need to explain another 0-0 draw five days after Saturday’s dismal stalemate at Liverpool.

Rashford has become adept at scoring big goals at important times for Mourinho; his extra-time winner against Anderlecht in April secured the subsequent last-four game against Celta, so the last thing United need is to be without the 19-year-old for any length of time.

Speaking less than half an hour after this Group A win in Lisbon, which leaves United just one victory away from qualification for the knockout stages, Mourinho admitted that he hoped for positive news on Rashford’s injury.

“I thought it was cramp because he was running so much and maybe had fatigue,” Mourinho said. “But he told me it was his knee. I hope it is not a big thing. It did not look it, but he felt something in his knee. I hope it is nothing important.”

Rashford was in obvious discomfort, however, as he looked over the bench and removed his shin pads. After a brief period of treatment, he limped off the pitch and down the tunnel, so United will now await the results of tests Thursday before discovering the extent of the problems.

At this stage, the England forward would appear to be doubtful for Saturday’s trip to Huddersfield Town, and the injuries are beginning to mount for Mourinho.

There is still no return date for Paul Pogba, who has been sidelined for five weeks now with a hamstring injury, while Eric Bailly, Marouane Fellaini and Michael Carrick are also not expected to figure at the weekend.

“I never speak about injuries,” Mourinho said. “Other managers cry and cry and cry, but I don’t cry.

“The way to do it is ignore the players who are injured, give confidence to the players who are available. I can cry for the next five minutes with no [Zlatan] Ibrahimovic, Pogba, Fellaini, Marcos Rojo, I can cry, but I don’t, so we do it with what we have.”

Losing Rashford will be as big a blow as being without Pogba, however.

The teenager scored his sixth goal in 13 appearances this season with the 35-yard free kick that Svilar carried over the line, but his goals are not the most impressive part of Rashford’s armoury. It is the youngster’s ability to change the tempo of games and lift United out of their slumber with a burst of pace or moment of inspiration.

As a second-half substitute at Anfield, Rashford was not able to influence the game against Liverpool, but his ambition and drive saw him transform United in the second half against Benfica and lift them to victory.

Romeul Lukaku scores more goals, and Anthony Martial has shown glimpses of his ability to make a difference from the bench, but Rashford is United’s talisman, and he is only going to get better.

Comparisons with Kylian Mbappe have been made, and they are not without foundation. The French forward is perhaps ahead of Rashford because of his record in the Champions League with Monaco and Paris Saint-Germain, but Rashford has similarly potent qualities.

He is Mourinho’s real game-changer, and though questions remain over Lukaku’s strike rate against top-quality opponents, Rashford can already point to winning goals against Manchester City, Arsenal and Chelsea in his career.

And he once again elevated a disappointing performance into a victory with his goal against Benfica, which has given United the chance to seal qualification against the Portuguese at Old Trafford on Oct. 31 — Rashford’s birthday.

“We are happy, we won the game, have nine points and no goals conceded,” Mourinho said after the game. “The team was compact and controlled. We are almost there — one point, one victory — to go through.

“We were in control. David De Gea did not have one save to make. I never felt we could concede a goal and were solid defensively.”

It is now 10 wins from 13 games this season, with Real Madrid inflicting the only defeat in the Super Cup in August.

United haven’t been pretty at times, but Rashford has helped turn draws into wins, and they cannot afford to be without him for long.

Mark Ogden is a senior football writer for ESPN FC. Follow him @MarkOgden_