American skiing standout Mikaela Shiffrin had an unexpected split with her longtime coach, Mike Day, during the middle of the world championships after informing him that she planned to take a new direction with her staff at the end of the season.

"Mikaela wants to do something different going forward. She wants a new challenge. And she informed Mike and Mike decided to go home," U.S. Alpine director Patrick Riml told The Associated Press on Wednesday. "It's a shock for me that he took off."

Day was with Shiffrin when she won the silver medal in super-G last week and then accompanied the skier for a few days of off-site training in Orcieres before returning to Meribel with her this week.

"He left yesterday," Riml said. "He's on the plane probably now."

Shiffrin, 27, was due to race again in her favoured events of giant slalom on Thursday and slalom on Saturday.

"After working with Mike Day for seven seasons, I've decided to move forward with new leadership on my team for the next phase of my career," Shiffrin said in a statement released by the U.S. ski team. "I want to thank Mike and acknowledge all of his work and dedication over the last several years."

• Canada earns team parallel bronze at alpine worlds

Day led Shiffrin's individual team within the U.S. squad. Shiffrin's team is also led by her mother, Eileen, who has coached the skier her entire life.

Shiffrin's personal team also includes new assistant coach Mark Mitter, who remains with her, Riml said.

Paul Kristofic is the head coach of the overall U.S. women's team.

"We've got plenty of people here to support Mikaela and provide the training and the information she needs on race day to do her job," Riml said. "She's got great support. ... We'll decide together what makes the most sense moving forward."

Day did not immediately respond to a request for comment from the AP.

Shiffrin is also in the middle of a record-breaking season on the World Cup circuit, having eclipsed Lindsey Vonn's record of 82 World Cup wins among women and moved within one victory of Ingemar Stenmark's overall mark of 86 wins.

Day worked with Shiffrin for 65 of her 85 World Cup wins, having coached her since July 2016.

It's not the first time Shiffrin has parted ways with one of her coaches midseason. Last year, assistant coach Jeff Lackie was removed from her team shortly before the Beijing Olympics.

The silver in super-G ended a troublesome run for Shiffrin in major championship races after she straddled a gate during the slalom run of the combined event in her opening race at worlds and didn't win a medal in any of her six races at last year's Beijing Olympics.

"Mikaela Shiffrin will be moving forward with new coaching, and will continue to be supported closely by the Stifel U.S. Alpine Ski Team coaches for the remainder of the season and in the future," the team said in a statement. "The team thanks Mike Day for his work and great success over the last seven years."

• The McKenzie Top Peak Ski Report keeps you updated on all things alpine

• Norwegians crowd parallel podium at alpine worlds

It's been a hectic week for Shiffrin since the super-G. She was targeted by a small protest from environmentalists who thought she wanted to travel by helicopter between her off-site base in Gap and the training slope in Orcieres, which was a 40-minute drive away.

The Orcieres ski club and a helicopter company had offered the use of a helicopter but Mitter told them from the start that she wasn't interested, said Megan Harrod, Shiffrin's spokeswoman.

"They made up stories," Riml said. "She always planned on driving up and down."

Because of the concerns about the protest, however, security was brought in to protect Shiffrin, Riml said, although Harrod added that the skier "didn't even hear" the protest.

Riml said he didn't think the helicopter flap had anything to do with Day's departure.

After the world championships end this weekend, Shiffrin will resume World Cup racing next month. The season ends in mid-March.