Olympic champs Tessa Virtue and Scott Moir of Canada withdrew from Four Continents last week because Virtue felt a tightness in her quadricep. This had nothing to do with the shin surgery that kept the team out of the beginning of the season. Unsurprisingly, Virtue and Moir are still good to train for and compete in the world championships.
I think it's likely that they were taking extra precautions, since Four Continents is not exactly a major crown for them and the world championships are coming up, and they have been so hampered by injury this season and in the past. It doesn't sound like the quadricep strain is something that bothers her anymore, from this article. But, oh, the drama! This makes worlds an even bigger mystery - assuming everyone skates clean, who truly does have the edge between Virtue and Moir and Davis and White?
And should either pair be scared about the prevalence of level 3 marks (rather than the highest, level 4) on their scorecards? In the short dances, Virtue and Moir got one level 3 while Davis and White got two level 3s, and were not happy about it. Davis and White also got two level 3s in their free dance, while Maia and Alex Shibutani had only one. They'd received higher levels on the moves all season but ice dancing judges are sticklers. It seems like either Davis and White are accidentally sacrificing technique in the heat of the performance, or the international judges are setting the stage for another worlds silver medal for the pair.