Ruben Amorim admits that he's 'really concerned' about after the star . De Ligt, 25, was making his first start since April 1 but hobbled off just 35 minutes into .

The Dutch centre-back collided with forward Yoane Wissa in the lead-up to the home side's second goal in the first half. On came , who De Ligt had replaced on Thursday as United saw out away to Athletic Bilbao in the semi-finals.

Amorim is now sweating on the 25-year-old's fitness ahead of the second leg on Thursday, but he's also concerned that De Ligt could be ruled out for months. Speaking to , the Red Devils boss was asked to provide an update.

"I don't know so I'm really concerned," Amorim replied. "Not about Thursday - we took off at half-time to protect and have players for Thursday - but I'm more concerned whether it is a small or big injury and thinking about next season."

Amorim confessed that his squad isn't 'ready' to compete in both the and yet, with injuries blighting his first half-season in charge. United's only chance of qualifying for the Champions League is by winning the Europa League final later this month.

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"We are not ready to play Premier League competitive and be in the Champions League, but we need to win and we need to win this competition to give something to our fans," Amorim vowed. "Then we will have time to prepare the team to cope with those two competitions."

Despite the result, which leaves United rooted to 15th in the Premier League table, Amorim sees the signs of a team who are improving game by game. "I have no doubt that we are playing better," the Portuguese said, having made eight changes to his starting XI in light of Thursday's crucial game.

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"So we have to take all the heat. At this moment we are losing games in the Premier League. We are fighting for the Europa League and Thursday is the most important game for us."

He added on the Brentford loss: "We started well, we controlled quite well and then throw-ins and set-pieces was a problem for us, but that is normal for us because we didn't have the height with the team. We fought back and we were near - we tried to push and in the end we lose."

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