The Oklahoma State men's golf team was missing a player this weekend at the Boilermaker Invitational. Freshman Casey Wittenberg (Stats | Bio) , who leads the Cowboys in scoring average, had a previous engagement at Augusta National Golf Club.

The 19-year-old amateur shot a record 31 on the back nine to finish the Masters Tournament tied for 13th at even-par.

As the low amateur, Wittenberg earned dinner Sunday night with Masters champion Phil Mickelson (Stats | Bio) and Augusta National members. He also won a sterling silver cup, and his top-16 finish brings him back to the Masters next year.

"It's kind of indescribable right now how I feel," said Wittenberg, who shot 69 on Sunday. "It's just a spectacular week."

Indescribable, unbelievable, storybook, spectacular, great. It's been that kind of tournament for Wittenberg, the runner-up at the U.S. Amateur. After shooting 4-over-par 76 in the first round, he had to fight to make Friday's cut. He shot 72 to get to Saturday, where he shot 71.

Then came Sunday. Wittenberg shot 38 on the front nine before ripping through the back nine at 5-under-par 31. It's the lowest back-nine score by an amateur in the tournament's history.

Six players, including Mickelson, held the previous record at 32. Wittenberg eagled for the second time in the tournament on the back nine, marking the first time an amateur made multiple eagles since 1959. His 13th-place finish is the best since 1962, when Charles Coe tied for ninth.

"It just shows you when you're out there you just can't ever quit, you've got to keep grinding it out," Wittenberg said.

The fans certainly appreciated Wittenberg's finish. As he approached the 18th green to putt for birdie, the crowd stood and cheered. The fans rose to their feet again once Wittenberg sank his par putt and walked off the green.

His caddie and father, Jimmy Wittenberg Jr., struggled to keep his emotions in check.

"It was pretty cool, it really was," he said. "You almost have to not think about it; I'll start crying."

Brandt Snedeker (Stats | Bio) , the only other amateur to make the cut, didn't have quite the success Wittenberg had, but he shared the experience. He tied for 41st at 12-over par after shooting 77 on Sunday.

"It would've been worth about a two-year wait," Snedeker said.

The 23-year-old was referring to the nearly nine-month wait from the time he won the U.S. Amateur Public Links championship until this week at the Masters. Snedeker had to wait until after this weekend to turn professional in order to keep his invitation to the Masters. He said he plans on turning pro today.

Wittenberg doesn't have plans to turn pro just yet. He still has to fly back to Oklahoma State to help the Cowboys prepare for the Big 12 championship, which begins April 26.

"I had a great time coming here this week and doing well, but now I've got to go back with my teammates and finish out the college year and see where it goes from there," Wittenberg said.

Reach Kristy Shonka at (706) 823-3219 or kristy.shonka@augustachronicle.com.