Lineker (left) scored 21 goals in his first season at Barca
Former Barcelona striker Gary Lineker has warned Manchester United that Thierry Henry may return to haunt them in the Champions League semi-final.
Ex-Arsenal star Henry has struggled to find his form since moving to the Nou Camp but BBC sports presenter Lineker believes that could change quickly.
Ahead of Wednesday's first leg, he told BBC Sport: "Big games give you a chance to convince critics and even yourself.
"Form can return just as quickly as it can disappear."
United go into the away leg as favourites to progress.
The Catalan club have endured a difficult season and Europe remains their last real hope to collect some silverware.
Henry's form has been a particular worry for the club, who invested £16.1m to bring the Frenchman over to La Liga in June 2007.
Lineker knows full well the pressures of performing at the Spanish giants, having spent three seasons at Barcelona after a £2.2m move in 1986.
In contrast to Henry, he was an instant hit with the fans after an opening campaign that resulted in him scoring 21 goals, including a hat-trick against their bitter rivals Real Madrid.
"It is a unique, special place," added the former England striker.
"They call it 'mes que un club', which means more than just a football club, and it is really.
"It is a way of life, it is quite political and consequently they don't have a lot of patience with players. It makes the extremes of success and failure greater.
"When you are doing well you are the king and when you're not you are hopeless, even more so than in England.
"There is an aura and the fans need to be entertained. It is not like in England where the fans get up and sing, you have to get them off their seats. It is different even to other grounds in Spain - it is more like a theatre crowd.
"You can be playing for 20 minutes and wonder if there is even a crowd in at all when there are 100,000 people.
"But for someone like Henry that should be right up his street because he is such a wonderful talent."
Things turned sour for Lineker in his third season when he was played out on the wing following the arrival of manager Johan Cruyff.
Henry has endured a difficult year at Barcelona
Henry has also been forced to spend the majority of this campaign out of position on the left wing to suit Barcelona's 4-3-3 formation.
Lineker said: "I was fortunate in that I had a good start, which always helps. I'm a lot different to Henry, he is a much better player than I was.
"I was predominantly a goalscorer and I nudged in with a couple of goals early on, which did take the pressure off, but Henry is different because he is creative and skilful.
"You get a different manager to the one that wanted you in the first place. In my third year Cruyff came in and wanted his own players so he nudged me out a bit and played me on the wing.
"It was a bit of a frustrating time so I know what it is like when things aren't going right but that's the nature of sport. You get good spells and you get bad spells whoever you are."
Lineker feels there is more to Henry's inconsistent form than being forced out on to the wing but has no doubts he can rediscover his best form if the Frenchman is given time.
"To go in and settle in a big team with great players takes time no matter where you are," said Lineker, who also played for Leicester, Everton and Tottenham.
"I think you will have to wait until next season to see the Henry that we know so well.
"Barcelona is a different environment, a different pace of play. He has gone from being the big fish to being one of the big fishes.
"He was always the fulcrum of Arsenal's play. He's not the linchpin. He used to be a winger when he was younger and it's not a difficult position compared to where he was playing but it's probably not giving him as much satisfaction or involvement."
Barcelona insist that there is no truth in newspaper reports that Henry could be on his way out of the club at the end of the season.
But Lineker said: "The Barcelona press always talk like that every week anyhow. Barcelona have such prodigious talents there that you never know.
"It's one of those places that if it is not going well then it can be quite difficult because the pressures can mount but I think he has such ability that he should be able to turn it around."
In his last game against United, in January 2007, Henry scored a last-minute winner and Lineker believes that a similar performance would go a long way to changing the opinion of him.
He added: "A couple of Champions League semi-finals and maybe a final and he could suddenly be the biggest, most successful, wonderful person in the history of the club. That is how it works."
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