Michael Thorbjornsen announced Wednesday that he will miss the U.S. Amateur, as well as the Walker Cup, due to a stress fracture in his back.

There was no mention of surgery, with the Stanford star saying in an Instagram post that his medical team has recommended a period of inactivity for the fracture to heal properly.

The No. 2-ranked amateur in the world will miss out on Cherry Hills C.C., where the U.S. Amateur is being contested next week, but the real sting comes from being unable to participate in this years Walker Cup.

The Walker Cup will be played the first weekend of September on the Old Course at St. Andrews.

It hurts missing our national amateur championship and not representing team USA at St. Andrews, but Im very grateful to the USGA for the honor and their support, Thorbjornsen said.

The 21-year-old was one of four co-medalists a year ago at the U.S. Am., alongside Fred Biondi, Luke Gutschewski and Hugo Townsend.