UEFA CHAMPIONS LEAGUE SEMI-FINAL:EVEN A QUICK glance at the squad lists and you know these teams have the attacking talent required to win tonight's intriguing semi-final at Old Trafford. Who has the defensive strength required to contain their opposition is, however, a different matter altogether.
Key to both sides' prospects will be the centre halves who will wear the captain's armbands. It is an occasion on which Carles Puyol can copper-fasten his reputation as one of Europe's greatest defenders and Rio Ferdinand can stake his claim to a place among that group.
Oddly, the pair have both been linked during their careers with the other's club.
A devoted Barca fan since childhood, Puyol once volunteered to be sold to United if the move would help the then heavily indebted Catalans claw their way out of financial trouble.
Ferdinand's move to Old Trafford was actually precipitated by Leeds United's disintegration but much more recently it had been suggested he was a target for the Spaniards as they prepare to start the reconstruction of their jaded looking side over the summer.
Puyol's background - he grew up in a nearby town and played for Barca from an early age - all but ensured he would be a favourite among supporters.
And his dedication to the cause over the years has sealed the deal, the 30-year-old defender showing huge passion for the cause in addition to the pace, strength and remarkable reading of the game that have marked him out as the sort of defensive rock upon which an attacking approach like Frank Rijkaard's can be constructed.
In a troubled season at the Camp Nou, Puyol has retained his immense popularity but has not been entirely blameless as the club's La Liga campaign hurtled off the rails. While the impending departure of Ronaldinho, Thierry Henry's inability to make an impact and Lionel Messi's injury problems have all made the headlines the defence has quietly crumbled behind them.
Barcelona have surrendered the title to arch rivals Real Madrid by taking just eight points from their last nine league outings. Puyol, though, remains upbeat about the prospect of victory this evening.
"We've had key players injured at different times," he says. "Not just one but two, three or four. Some important ones are back now so we're confident of doing well at Old Trafford.
"They have some of the best players in the world," he continues. "Cristiano Ronaldo, Rooney and Tevez can all win a game. United's strength is its attack so it's up to us to stop them. It's a challenge but I like playing against English sides because the game always has a high intensity."
Intensity would probably not be one of the things Ferdinand likes most about games but the 29- year-old has come a long way since Alex Ferguson signed him almost six years ago as part of an ongoing attempt to hit upon a central defensive partnership capable of serving the club in the way the Bruce-Pallister one did.
Ferdinand is almost three inches taller than Puyol and is probably the more gifted of the pair with the ball at his feet.
For years, though, he struggled to win over supporters, who tended to dwell on his regular blunders rather than the elegance of some of his passing.
With Nemanja Vidic at his side, though, Ferdinand has really started to look the part this season.
In the first leg he was outstanding even without his regular partner but his loss of composure towards the end of Saturday's game at Chelsea suggested there is still a vulnerability about him under pressure.
Without him 12 months ago, however, United, were well beaten by Milan at this stage of the competition and if Barcelona's gifted front line can be subdued tonight in the way it was last week he will have made a strong case to join Puyol in defending's top drawer.
