Phil Jones is the latest player to give England manager Roy Hodgson an injury selection headache, just less than a week before he names his squad for Brazil.
The defender has nine England caps to his name already and was expected to be named as one of Hodgson's final 23-man squad next week, but his place in the squad is now in jeopardy - due to a potential shoulder injury.
Jones hurt himself during a mid-air collision with Maynor Figueroa - in the first half of Manchester United's 3-1 win over Hull City last night - and was rushed to hospital to have an X-ray on his shoulder.
United interim manager Ryan Giggs stated that the way in which the 22-year-old reacted following the clash gave him an immediate cause for concern.
Speaking after the game, Giggs said: "He has gone to hospital. We will just have to assess it and see how it goes, but it didn't look great.
"Just by his reaction, he knew he had done something and he wanted to come off. Usually, as a player, you know that something is not great when you do that."
When quizzed about the chances of Jones being available for World Cup selection, Giggs added: "I don't know. The reaction, he asked to be substituted straight away. Whether it is precaution (I don't know) but, hopefully, it is not too bad."
Should he be ruled out, Jones will join Theo Walcott, Andros Townsend and Jay Rodriguez on the side-lines for the summer. Meanwhile, Kyle Walker is also a doubt - after missing the last two months of the season with a pelvic injury - but there is some hope that he might just recover in time to be included.