Argentina and Barcelona attacker Lionel Messi admits he was dumbfounded by the decision not to take Theo Walcott to the World Cup.
Walcott was expected to make the plane to South Africa but England manager Fabio Capello opted to leave him at home.
The decision came despite the fact that the 21-year-old became the youngest player to score a hat-trick for England in 2008, following an excellent performance in Croatia.
And Messi points to last season's UEFA Champions League clash between Arsenal and Barcelona as another match where Walcott had a major impact.
With the Gunners trailing 2-0 and on the ropes against the Spanish champions at the Emirates, Walcott came off the bench and changed the game as Arsenal salvaged a 2-2 draw.
Messi, 23, was shocked when Capello named his World Cup squad, and believes England would have had more success if Walcott was onboard.
"I must say that at the time I thought it was a bad decision to leave Theo Walcott at home," he told the Daily Star.
"And I think that has been proved right. I can only speak from experience but he was one of the most dangerous players I have ever played against.
"Barcelona players are not scared easily but I can tell you that when we played Arsenal last season he truly worried us.
"When we were playing Arsenal at the Emirates we were so in control of the game at 2-0, with all respect Arsenal were not even in the game.
"Then Theo came on and changed the game. He pretty much single-handedly salvaged a draw against Barcelona that night.
One to watch
"Even in the return leg our manager Pep Guardiola was telling us he was the player to watch out for.
"And the best players in the world like Xavi and Gerard Pique were telling us to watch out for him. The truth is that he really rattled him.
"If he could do that against Barcelona, think what he could have done against Germany and Algeria. Even if he didn't start, he would still have been very important for England.
"Along with Cesc Fabregas and Sergio Aguero he would have been the best impact player at the World Cup."
Messi, whose Argentina side crashed out in the quarter-finals after also being thumped by Germany, says Walcott's pace is his best asset.
He added: "Even at the top level, pace scares the world's best defenders. And, take it from me, he would scare any defender.
"When England brought on players, I don't think they were at the level to make any impact. But Walcott would have been and I still can't understand why he wasn't taken.
"He is a big-game player as well who rises to the occasion. He scored a hat-trick in Croatia, which nobody ever does and was the star against Barcelona."