Manchester United are just too shaky from set pieces, as Simon Kjær’s 92nd-minute equaliser illustrated. Switching off at dead balls is an unwanted theme of their season, and on this occasion lax positioning while defending a Milan corner and Dean Henderson’s soft hands were culpable. When Anthony Martial’s hip injury is factored in – the striker needs a scan to determine its seriousness – this was a particularly difficult night for Ole Gunnar Solskjær’s side. Martial joins Marcus Rashford as a doubt for West Ham’s visit this Sunday, with a third forward, Edinson Cavani, also ruled out, according to the manager. While Solskjær is hopeful Rashford, at least, could return for Thursday’s second leg at the San Siro, Milan were certainly worthy of their vital away goal. Stefano Pioli’s side were always positive and, for large swathes, the dominant force. It means United are now underdogs to progress to the quarter-finals. Solskjær is always keen to defend his team but was unable to regarding Kjær’s late intervention. “It’s a header from six yards – he can save it, of course,” the Norwegian said of Henderson. “I have seen him save them but it’s the structure [overall] we lose. We dropped too deep and get blocked off and he [Kjaer] makes a good run and gets a good header on it. We should have attacked the ball with the men we had there. “I am very disappointed to concede like that with the header. It makes it harder of course, but it was always going to be going down to the second game.” Of Martial’s injury, Solskjær said: “Ant has a whack on hip – it’s another forward we need to scan and look at. Definitely hope he’s back for Thursday but I’m not sure for Sunday, we’ll need him. Don’t think Edinson will be ready for Sunday. Marcus will be ready for next Thursday. I am not sure if he will be ready for the weekend – fingers crossed. And Cavani maybe, as well, for the Milan game.” Milan arrived in the mood to force the issue, and their pressing inside United’s half caused problems. What Solskjær’s side did not need to do was switch off, which they did when Davide Calabria’s throw-in was allowed to reach Franck Kessié. His 20-yard strike gave Henderson no chance but, after a delay, VAR ruled the midfielder had handballed to control. United remained in slumbering mode when Rade Krunic swept in a long free-kick that no red shirt wanted to claim aerially. Milan were caught offside but what United required were smelling salts to jolt themselves awake. There was zero pattern to their play. Instead, the visitors tapped the ball around in a manner that had the feeling of a schooling for United. When Bruno Fernandes could finally look ahead in possession, his intended pass was too short and the attack fizzled out. Instead, Calabria could thrust from right-back into United’s area to cause havoc, and the home side escaped again in what was becoming a Harry Houdini-act of a half. Their next close shave came when Martial jumped out of a challenge near Milan’s area. Suddenly, Brahim Díaz broke fast, Alexis Saelemaekers took over and cut inside from the right. Henderson’s fingers were warmed by his fierce effort. At that point, Harry Maguire shouted to his teammates to stop giving the ball away. The captain might also have implored his team to get out of backward gear, fast. But they did start to brighten and soon went close to an unlikely opener. Alex Telles swung in a corner from the right which Fernandes flicked on. He looped the ball over Gianluigi Donnarumma, who managed a faint touch, before Maguire hit the post from inches. The ball went across goal but somehow stayed out, and the score remained goalless. “I won’t make any excuses for that,” the centre-back said. “I should put it in the net.” At the break, Solskjær replaced the injured Martial with Amad Diallo, who was about to have a dream impact. Fernandes earned a free-kick in a central area and passed to Nemanja Matic, who gave the ball back to him. The Portuguese looked up, spied Diallo’s clever inside-right run and expertly chipped it over. The youngster’s flick past Donnarumma oozed class. It was a fine way to open his United account, and Milan were stunned. Their response was to bombard Henderson’s goal, with Pioli’s team feeling they should have had a penalty when Aaron Wan-Bissaka reached over Díaz to head clear and the latter went down. As a spectacle, the contest continued to improve. Calabria zipped over a cross which Krunic flung his head at, connecting with the ball but unable to keep it down. Then United offered a rare counterpunch when Greenwood combined with Diallo, before finding Dan James in space. The winger was under no pressure, but his control faltered. The closing minutes began in a squall that made composed play tricky. But then came Kjær’s header. It dazed United, who have much work to do next week: more regulation errors and they may be out of Europe.