Eric Byrnes has opted against surgery on his torn left hamstring muscle, although he admitted Friday that even then there are no guarantees for his return this season.

"I'm not going to be crazy. It's something I'm going to be real cautious with," Byrnes said.

"I'm not saying I'm rehabbing to come back this year. I'm not going to rule it out. I'm just not sure how my leg is going to respond."

Byrnes has been out since July 1, and the D-Backs obtained Tony Clark in part to add the offense they have missed.

He said the doctors he spoke to were split on whether surgery was necessary, and that either way his hamstring would be as good as ever.

"Given that option, it was a no-brainer for me," Byrnes said.

Byrnes said the D-Backs suggested surgery but were supportive of his decision. He is expected to rehab with the D-Backs' training staff.

At the same time, surgery is not off the table if Byrnes' hamstring does not recover by October, because the D-Backs want to insure his availability for 2009 and surgery requires a 4 to 6 month recovery period. He signed a three-year, $30 million deal last year.

Byrnes said he came back too soon after a 27-day stint on the disabled list June 23.

"I told them I was ready. I thought I was. But I still had something in there," he said.

LOVE 1, MONEY 0

When it was apparent that neither the D-Backs nor San Diego would pony up $500,000 to pay Tony Clark's assignment bonus, Clark bit the bullet and basically paid it himself.

"It wasn't an easy decision to make," Clark said.

"Realizing that San Diego was making an opportunity for me to come back home, and that the Diamondbacks were a first-place team ... I had to make a decision if I wanted another opportunity here.

"I decided it was worth coming back."

Clark will wear No. 13, a number suggested by his wife, after playing in No. 34 his previous three seasons here. Conor Jackson took 34 this spring.

UPTON ON THE DL

Justin Upton was placed on the disabled list with a strained left oblique muscle Friday, retroactive to July 9, when he suffered the injury on a batting practice swing in Washington.

"He needed to take some violent swings in batting practice (Thursday), and he's not close to that yet," Melvin said.

Upton, who took a six-game hitting streak into his injury, is eligible to return July 25, when the D-Backs start a 10-game road trip on the West Coast, but Melvin said that "is probably a stretch."

SHORT HOPS

Chris Snyder (testicular fracture) hit a three-run home run in the third inning and was 2-for-5 with four RBIs in a rehab game for Single-A Visalia Friday. If Snyder recovers well, he is expected to be activated Sunday. ...

Left-hander Wade Miley, the D-Backs' sandwich pick in the 2008 draft, signed for a bonus of about $875,000 and will report to Single-A Yakima of the short-season Northwest League. Miley was 7-3 with a 3.90 ERA at Southeastern Louisiana, striking out 119 in 101 2/3 innings. He threw 158 pitches in one start in the Southland tournament, and like college starters Micah Owings and Wes Roemer, will be given a light workload this summer. ... Washington has made setup man turned closer Jon Rauch available in trade, but it is unlikely the D-Backs would be willing to meet the building Nationals' asking price, always prospects. ...

Right-hander Jake Barrett of Mesa Desert Ridge High and the entire USA Baseball Under-18 national team visited Chase Field as guests of the D-Backs on Friday. Barrett is one of seven pitchers on the U-18 team that will compete in the world junior championships July 25-Aug. 3 in Edmonton, Alberta.