Sergio Ramos gets harsh lesson as Danny Welbeck exposes Real Madrid's set-piece flaw

No-one will ever be able to say that Jose Mourinho did not compromise his style when he went to Real Madrid. In recent history the team have been defined as much by defensive frailty as by their attacking verve and the former Chelsea manager has embraced that, unable to stem the tide of goals scored from set-pieces.

The finger of blame for this season's goals conceded from corners and free-kicks had been pointed at goalkeeper Iker Casillas and his reluctance to come off his line. At the Bernabeu he was absent but still Real conceded Manchester United's all-important away goal from a corner. The weakness will encourage Sir Alex Ferguson ahead of the second leg at Old Trafford.

Speaking about the United forward line in the build-up to the match, Real captain Sergio Ramos told me about the strengths of three of United's attacking players. He raved about Robin van Persie's ability to change a game with a moment's magic. He spoke about his ferocious shot, released so quickly and from both feet. Ramos moved on to Wayne Roooney and talked about the dilemma he creates for defenders roaming deep and wide, leaving the defensive player wondering how far he should go to follow him. And he praised Javier Hernandez' ability to score two or three goals in brief substitute's appearance. He never mentioned Danny Welbeck.

But Ramos found himself marking the England striker when Rooney's corner came in and Welbeck got the better of the Spain international to make it 1-0. The last player to score from a header against Real Madrid in the Champions League knockout phase was Yossi Benayoun for Liverpool four years ago. But this was standard set-piece defending from Real Madrid this season.

Casillas has been replaced by a taller keeper who is more confident in coming for balls hung in the air. Diego Lopez was on United's shopping list when he was playing for Villarreal in the Champions League and Ferguson was looking for a long-term replacement for Edwin van der Sar.

He was helpless as Real's Achilles heel was their undoing again. Ramos was accompanied by 19-year-old Raphaël Varane in central defence with Pepe left on the bench. An early loose back pass from the former Lens teenager underlined the communications problems at the back for Real – that are repeated at set-pieces.

Pepe and Ramos were involved in the most famous of Real Madrid's corner failings last season when Ramos had been told to pick up Carlos Puyol at corners during a match with Barcelona. The pair had swapped for one corner and Pepe had been beaten in the air by Puyol as Barça scored. The training ground inquest brought the infamous exchange between Mourinho and Ramos – "So you think you're the coach now" followed by "You never played the game so you wouldn't know."

After yesterday's slip it will be back to the drawing board at Valdebebas ahead of the second leg.

Mourinho's other concern before that second game will be the ongoing lethargy of his forwards. Karim Benzema is like Lopez, another player who interested United. Ferguson decided ultimately that he was over-priced and that allowed Real to sign a player president Florentino Perez hoped would be his new Brazilian Ronaldo.

When he needed to be at his best he showed all the lack of aggression that has hindered him this season. He has never been the archetypal Mourinho No 9 and it has shown itself most in the biggest games since the Portuguese manager took over. It was apparent once again. He was replaced just before the hour by Gonzalo Higuain and the Bernabeu roared its approval at the change.

Higuain's first contribution was float a harmless shot over David de Gea's bar. He too has been short of the standard desired by Mourinho hence the decision to start the Frenchman.

How Ronaldo might benefit playing off of a dominant centre-forward the club may end up finding out next season – they will look to bring in a new No 9 in the summer. Though Mourinho being around to reap the benefit is far less likely.