Two English teams are in action on Wednesday night, with both fixtures too close to call.
Manchester United travel to Porto with the tie at 2-2 after an excellent performance by the Portuguese team at Old Trafford in the first-leg. Five years ago United were dumped out of the competition by Porto at exactly the same stage and Alex Ferguson's men will be desperate to avoid a repeat. The Manchester United manager has stated that he feels he has a score to settle.
Click the image on the right to launch our guide.
The other quarter-final will see Arsenal entertain Villarreal. The match is a repeat of the 2007 semi-final in which Arsenal came through before losing in the final to Barcelona. Arsenal secured a 1-1 draw in Spain thanks to a magnificent strike by Emanuel Adebayor. Will his away goal prove decisive?Reuse content