Match ends, RSC Anderlecht 1, Manchester United 1.
Manchester United were left to rue missed chances as Anderlecht salvaged a late draw to change the complexion of their Europa League quarter-final tie.
Leander Dendoncker got in front of Matteo Darmian to head an equaliser with the Belgian side's first effort on goal four minutes from time.
Until that moment United had subdued the hosts, and deservedly led when Henrikh Mkhitaryan tapped in from a tight angle after Marcus Rashford's shot was spilled in the first half.
But the Armenian side-footed wide when well placed after the break and Paul Pogba fired into the shins of goalkeeper Ruben to leave Jose Mourinho's side vulnerable to the sucker punch landed by 21-year-old Dendoncker.
- 'I have no better word than sloppy' - Mourinho blames his attack
- Relive Anderlecht v Manchester United
Improved United undone by late mistake
United's Europa League odyssey this term has taken in disappointing evenings away to Feyenoord, Fenerbahce and Rostov, and Mourinho's frustration in Brussels will centre on a decent performance undermined by lax finishing and a late defensive lapse.
Since his last foray into second-tier European competition in 2003, the Portuguese has become accustomed to the bright lights of the Champions League, winning it twice and disparaging predecessor Rafael Benitez's Europa League success after taking over at Chelsea in 2013.
But United's position in the Premier League - four points off the top four with games running out - has forced him to revise his attitude.
For most of the match, his team seemed focused on the task. Just five games away from booking a return to the Champions League - Uefa's sweetener for winning the competition - they looked solid in defence and slick in attack.
For their part, Anderlecht's enterprising young team offered little, deprived of possession and restricted to efforts from distance - but all that changed with Dendoncker's late goal.
United will still fancy their chances of finishing the job at Old Trafford next week, but with more dangerous opponents elsewhere in the draw - notably Lyon and Schalke - similar mistakes could easily derail their progress to May's final.
Mourinho claimed that his attackers let down their defensive colleagues in his post-match interview, but it seemed harsh to burden Rashford with a share of the blame after one of his brightest performances of the season.
The 19-year-old - whose goal return was recently questioned by Mourinho - was heavily involved before being replaced by Marouane Fellaini in the 75th minute.
He roamed dangerously from the left, tormenting full-back Dennis Appiah and threatening with a dipping shot from distance before creating the opener as Ruben failed to grasp his sweetly struck shot
His industry in the opposite direction also caught the eye as he diligently tracked Anderlecht's runners.
It was the sort of all-around performance that Mourinho usually demands of his attacking players but, publicly at least, the boss seemed nonplussed.
Man of the match - Antonio Valencia (Man Utd)
Mkhitaryan goal return rivals Ibrahimovic
- Of players who have scored at least two goals, only Zlatan Ibrahimovic (134) has a better minutes-per-goal rate than Mkhitaryan (212) for Manchester United in all competitions this season.
- The Red Devils are unbeaten in their last four European away games (W2 D2), after losing each of the five before that.
- Leander Dendoncker scored with Anderlecht's only shot on target of the game.
- Paul Pogba attempted 127 passes in the game, the fourth-highest total by a player in a Europa League game this season. He is also second with 130 against Zorya Luhansk on 29 September.
Manchester United play Premier League leaders Chelsea on Sunday before the second leg at Old Trafford next Thursday. Anderlecht play KV Oostende on Sunday in the Belgian top flight.
- 37ObradovicBooked at 67mins
- 10BrunoSubstituted forChipciuat 58'minutes
- 73StanciuSubstituted forHanniat 65'minutes
- 24ThelinSubstituted forTeodorczykat 75'minutes
- 25A Valencia
- 16CarrickBooked at 47mins
- 14LingardSubstituted forMartialat 63'minutes
- 22MkhitaryanBooked at 24minsSubstituted forFosu-Mensahat 90+1'minutesBooked at 90mins
- 19RashfordSubstituted forFellainiat 75'minutes
- 1de Gea
- Dr. Felix Brych
- Shots on Target
Second Half ends, RSC Anderlecht 1, Manchester United 1.
Corner, Manchester United. Conceded by Ivan Obradovic.
Paul Pogba (Manchester United) wins a free kick in the defensive half.
Foul by Leander Dendoncker (RSC Anderlecht).
Timothy Fosu-Mensah (Manchester United) is shown the yellow card for a bad foul.
Foul by Timothy Fosu-Mensah (Manchester United).
Sofiane Hanni (RSC Anderlecht) wins a free kick in the defensive half.
Foul by Antonio Valencia (Manchester United).
Frank Acheampong (RSC Anderlecht) wins a free kick in the defensive half.
Substitution, Manchester United. Timothy Fosu-Mensah replaces Henrikh Mkhitaryan.
Foul by Marouane Fellaini (Manchester United).
Youri Tielemans (RSC Anderlecht) wins a free kick in the defensive half.
Attempt missed. Paul Pogba (Manchester United) right footed shot from outside the box is too high. Assisted by Anthony Martial.
Goal! RSC Anderlecht 1, Manchester United 1. Leander Dendoncker (RSC Anderlecht) header from the centre of the box to the bottom left corner. Assisted by Ivan Obradovic with a cross.
Offside, Manchester United. Zlatan Ibrahimovic tries a through ball, but Anthony Martial is caught offside.
Attempt saved. Marouane Fellaini (Manchester United) header from the centre of the box is saved in the centre of the goal. Assisted by Henrikh Mkhitaryan with a cross.
Corner, Manchester United. Conceded by Rubén Martínez.
Attempt saved. Paul Pogba (Manchester United) right footed shot from the centre of the box is saved in the bottom left corner. Assisted by Zlatan Ibrahimovic with a through ball.
Attempt missed. Sofiane Hanni (RSC Anderlecht) right footed shot from outside the box is high and wide to the right. Assisted by Alexandru Chipciu.