Last meeting: The draw in the Bernabeu was a fabulous advertisement for the game and engrossing stuff. Danny Welbeck silenced the home fans by heading in a priceless away goal, only for Cristiano Ronaldo to take off to nod home and cancel it out in stunning fashion. Both sides had chances to grab a winner with David De Gea in top form and Robin van Persie unable to take a couple of excellent opportunities.
Did you know? United have only progressed once on the away-goals rule in European competition - against Dukla Prague in the 1983/84 European Cup-Winners' Cup.
Opposition boss: Jose Mourinho needs no introduction after forging a reputation as one of the best coaches in the game. The former Chelsea chief has enjoyed success against the Reds with the Londoners and, before that, Porto and enjoys a good relationship with Sir Alex Ferguson. Known for his tactical acumen, he will be hoping to come up with the right game-plan for Old Trafford. Despite the speculation regarding Mourinho's future, Sir Alex thinks he could stay on past the summer.
Star man: Cristiano Ronaldo heads a galaxy of world stars and will look to follow up his goal in the first leg by scoring on his old stamping ground. The Portuguese star remains hugely popular with the United fans but it is acknowleged he is the biggest threat on the night. Some pundits feel Ronaldo is close to moving onto the same level as World Player of the Year Lionel Messi in terms of his consistency.