Former Reds and Barca player Jordi Cruyff has pinpointed the two world stars as the key figures in the Nou Camp and Old Trafford over the next seven days.
But Cruyff, who at 34 now plays for Metalurh Donetsk in the Ukraine, insists Ronaldo has the in-form back-up from the Old Trafford posse to win the duels in Spain and Manchester.
Messi has made only two substitute injuries since a month out with a hamstring injury and there are doubts whether he will start.
"Last season Kaka was the key man in the destiny of the Champions League trophy," Jordi told M.E.N. Sport.
"He was the best player in the world and was central to AC Milan's European Cup win. Well, I think this season for Kaka you can substitute Ronaldo.
"There is no doubt he is the key to United's success. You get players like this from time to time who just take things on a level.
Stage
"Three years ago it was Ronaldinho for Barcelona who helped make them the team they were. Kaka did it for Milan and now Ronaldo is at that stage.
"He did well last season but he wasn't quite up with Kaka. But I think Ronaldo has made that step forward.
"You need these strong standout players if you are going to win the Champions League.
"But not only that, you have to have class team-mates who are playing well and playing as a unit. United have that. They are a complete team.
"Sir Alex Ferguson has a side with pace and they have the firepower to get past Barcelona.
"If they had had a choice, then Barca would have rather played Chelsea or Liverpool because they believe United are unstoppable on their day."
In contrast to United's form and confidence as they ready themselves for a Premier League triumph, Barca's La Liga return has been poor and rivals Real Madrid are on the brink of securing a back-to-back titles to rub the Catalans' nose in it.
"United are undoubtedly the team on a high while Barca are on a low," added Jordi.
Problem
"Barca's hopes rest on Messi. He is an enormous talent without doubt but the problem in this case is, unlike Ronaldo who is fit and on top of his game, Messi only returned last Saturday for half a game after being out for five weeks with a thigh injury.
"He is the player who can keep them alive. They need him and he will play a big role and can make the difference. But the critical question is: is he ready for this kind of level of competition?
"If Messi, Deco, Samuel Eto'o, Andres Iniesta, Yaya Toure and Thierry Henry are on their game, then Barca have a chance but you have to say the pointers are not good.
"However, on the other hand, big teams can often save their best for the Champions League.
"Look at Milan last season they came alive in the European Cup.
"Big teams stand up on the big occasion and no matter the disappointments of La Liga, Barca have made it to the semi-final.
"I have friends at the Nou Camp but if you forced me to spend a few euros on a bet then I would have to go for United."
Cruyff had an injury ravaged United career from 1996 to 1999. He went on loan to Celta Vigo during the treble season, but he still sensed the feeling inside Old Trafford that they were on to something big.
"It is hard to describe the feeling in the squad in '99 but there was definitely something there," says Jordi.
"You just had this air and atmosphere around the club and the players on the training ground that it was a big year. You knew something incredible was about to happen.
"From what I hear from inside the club that same feeling is around the place now."
Who do you think is better, Messi or Ronaldo? Have your say.
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Showing comments 1 to 25 and replies | View All
Newton Heath F.C. (22/04/2008 at 09:23)
Come On You Reds......!
Janu (22/04/2008 at 09:45)
You just have to compare their actual form in the league. But when you see last years outcome for best player on the planet you cannot be sure what result their will be announced by the corrupt Uefa.
Anyway my prediction for the game is
Barca 2 - ManU 3 then ManU 3 - Barca 1
Viva la Reds
Janu, Cologne
Roy (22/04/2008 at 10:06)
Steve in Brussels (22/04/2008 at 10:22)
Frank Old Trafford (22/04/2008 at 10:30)
Gillian England (22/04/2008 at 10:36)
Ronaldo has the height and strength and is very fast
Lionel has the speed as well as being a very good forward
they are both so good
im going for Ronaldo cos i support Manchester United
GO UNITED
Demo, Glossop (22/04/2008 at 11:20)
come on united
mickle, midlands (22/04/2008 at 13:01)
messi is real quality - but barcelona are all over the place and we will dominate them.
Nacao Valente,London (22/04/2008 at 13:05)
ronaldo is the best player ever...just look,nobody was so complete as he is!
Glory glory manutd...
Red Dawn (22/04/2008 at 13:44)
Messi will turn up tomorrow night, Ronaldo won't.
I can see it now.....
Ronaldo constantly going down looking at the referee for a foul, waving his hands in the air wondering why he's not been given it. He'll give the ball away more often than a toddler.
Whats the betting Ferguson plays him up front on his own, which is only going to add to the frustration of a bad night that I predict 'once again' he will have against a top side.
I want him to prove me wrong tomorrow night and start proving it against the top sides, when it really matters.
The stage is set, so it's time to deliver.
Johnny The Truthful One Smith (22/04/2008 at 13:44)
Johnny The Truthful One Smith (22/04/2008 at 13:50)
mario (22/04/2008 at 13:51)
Well in the last few weeks he scored vs Roma than he scored vs Liverpool than he scored vs Arsenal. I guess to please some clowns he has to score in every game against every club. Even then there will be excuses from the haters, jealousy is the best form of flattery.
Ronnie7 (22/04/2008 at 14:26)
Steve in Brussels (22/04/2008 at 15:16)
Ronie is top scorer this year & has dominated as much as Kaka did last year aside from the semi against us. This could be his moment. I recall Messi memorably doing nothing against not only Chelsea but Liverpool as well. A game is 90 mins and depends on a variety of factors including luck.
Eric Cantona never quite achieved his best in Europe so does that make Steve McManaman a better player then because he turned up in a Ch L final?
Demo, Glossop (22/04/2008 at 15:32)
and yet despite all this greatness for us to enjoy you are so cynical and negative!
VALTINHO, LISBON (22/04/2008 at 16:08)
blue dum dawn.
Mark,verypleasedwithsvensofar. (22/04/2008 at 16:40)
Red Dawn (22/04/2008 at 17:12)
Ofcourse I am a united fan, but Ronaldo does not produce against the top sides, or when it really matters, that is a proven fact. Just because I'm not on the hype bandwagon or most people don't agree with my opinion, doesn't mean I'm not a United Fan. Call me Simon Cowell if you must..."Boooo" lol.
I'm a real United fan, and not a plastic who jumps on the ship when success occurs, or a plethora of foreign stars are signed.
Secondly, there is no such thing as the best player in the world. How do you compare different positions? You can't.
It's tabloid hype and bias towards attacking players and most of the time flair is seen as a deciding factor over true footballing abilty. You flick your leg over the ball a few times in a standing position, to no affect and suddenly your seen as a great player.
The way the awards should be worked is, you choose one player from each position each season and say he is the best player in the world in that position, for that season. That way it is balanced and fair.
I want Ronaldo to prove me wrong and rise to the occassion tomorrow night. Call me Nostradamus, but I've constantly predicted a poor game from Ronaldo prior to every game we play against a top side.
Is that just a coincidence, or maybe I do actually know what I'm talking about.
I don't care how many goals he's scored this season. If a so called great player cannot produce against the best sides, then he is not a great player in my opinion. Sure, you might have an off night here or there, but Ronaldo has never produced a world beater performance against a top side. I'm still waiting to see it, after 5 years, and I'll be the first to say well done if he does do it.
Valtinho,
Your opinion is always going to be biased towards Portuguese players anyway. Even when Ronaldo plays a stinker, you create an opinion to say he played well. You need to be a little more open minded. By the way, how long have you followed United?
Lastly, people need to stop bringing up the subject of who is better, George Best or Ronaldo?
This is absolutely ridiculous, and an insult to a truly great player that George Best was.
You can make comparisions, sure, but you don't bring up the question of who is better. George Best was aruguably the best player ever to kick a football, and for some to say a 23 year old kid is better than him at this stage of his career, is just insanity, an insult, and a disgrace.
Ronaldo has alot of steps to climb before you could put him anywhere near Bests level.
COLIN,, Canada (23/04/2008 at 01:42)
francis lee's bellybutton, manchester (23/04/2008 at 08:42)
AS, Ipswich (23/04/2008 at 09:40)
I can understand your feeling if you are a true red but RONALDO WILL DELIVER TONIGHT.
THAT BOY RONALDO, Manchester (23/04/2008 at 09:58)
Demo, Glossop (23/04/2008 at 10:37)
red dawn you go on about how can you pick a best player in the world and then go on to say best was the best player! im not disagreeing bestie was best but surely you have contradicted yourself?
Ok im going to make a prediction - ronaldo will have a stormer tonight and score 1 goal and get 1 assist!!
the reason ronnie struggles against better teams is because the opposition are better and usually double or triple up on him!
Frank Old Trafford (23/04/2008 at 11:41)