The Associated Press

SAN DIEGO — The U.S. Open, San Diego style, brought morning fog that clung to the cliffs and spilled over to Torrey Pines Golf Course when Tiger Woods showed up for another nine-hole session Tuesday.

The setting could not have been more appropriate.

What once had been such a clear picture of this U.S. Open is now shrouded with uncertainty, starting with the left knee of the No. 1 player in the world. Woods has not played a competitive round since his runner-up finish at the Masters on April 13, having surgery two days later to clean out cartilage.

Perhaps even more startling was that Woods has not walked 18 holes since then and most likely won’t until he steps to the first tee Thursday morning.

‘‘Is it fully recovered?’’ he said. ‘‘Probably not.’’

Woods played 17 1/2 holes last Wednesday in a cart, then retreated to his club in southern California for more cart golf over the weekend. Then came nine holes at Torrey on Sunday, Monday and Tuesday, and he typically doesn’t play at all the day before a major begins.