Zhang in for Casey at US Open
Teenage prodigy Andy Zhang will become the youngest player at the US Open since the Second World War after Paul Casey was forced to withdraw.
China-born, Florida-based 14-year-old Zhang narrowly missed out on qualifying for the major in a play-off.
However he gets his chance as Casey misses out through injury.
Having hoped he was over the shoulder dislocation he suffered snowboarding on Christmas Eve, England's former world No.3 is not yet fit for the rigours of a major.
"You're always disappointed to miss time due to injury, but it's especially true when you have to withdraw from the US Open," said Casey.
"I've been trying to play my way back and I feel like I probably came back too soon originally.
"It's affecting my ability right now to be ready for the test of a major. I do feel like I'm very nearly ready, but not quite ready for this week."
There is a chance of him playing at the BMW International Open in Cologne next week.
Casey missed the first two months of the season, but after four missed cuts in a row on his return - including The Masters at Augusta - things were looking up when he finished 25th in Korea in
But the 34-year-old then had to withdraw after nine holes of the Players Championship in Florida, pulled out of the Volvo World Match Play in Spain and shot rounds of 78 and 76 to miss yet another cut in the BMW PGA Championship three weeks ago.
That remains his last competitive action. He is down to 58th in the world rankings and likely to fall even further this week, while the odds on him returning to the Ryder Cup team - he was not picked by Colin Montgomerie two years ago despite being world No.9 at the time - are getting longer all the time.
Zhang was joined in the main draw by fellow amateur Jordan Spieth, a member of last year's American Walker Cup side in Aberdeen. The Texan takes the place of compatriot Brandt Snedeker, out because of a rib injury.