Giants trainer Dave Groeschner said that an angiogram Chulk underwent Tuesday at Sequoia Hospital in Redwood City, Calif., revealed that the right-hander has no blood clots, as initially suspected. Instead, doctors believe that Chulk is afflicted by Buerger's Disease, a rare circulatory ailment. If untreated, the illness can lead to skin ulceration and gangrene of the fingers and toes.

Groeschner pointed out that tobacco use is one of the main causes of Buerger's Disease. Chulk, like many ballplayers, uses smokeless tobacco, although Groeschner said that Chulk stopped once his discomfort began. Groeschner said that this habit, combined with the physical stress of pitching, led to the numbness, chilly sensation and discoloration in Chulk's right middle finger that symptomized the problem.

A blood clot might have meant season-ending surgery for Chulk, 28, who went on the 15-day disabled list Monday. But the revised diagnosis doesn't necessarily mean that he'll pitch again in 2007. "We're not going to rush through this," Groeschner said, indicating that Chulk will undergo further examinations and tests. "We're trying to be as thorough and complete as possible."

Here and now: The prospect of competing for the closer's job next Spring Training doesn't concern Brad Hennessey, who remains intent on the present.

The return of 2005 fill-in closer Tyler Walker and the ascent of right-hander Brian Wilson could mean that Hennessey, despite his ability to protect ninth-inning leads, will have to win his job all over again when the Giants reconvene in Scottsdale, Ariz.

But, Hennessey said, "I'm not really thinking about next year right now. I want to finish this year as well as I can and hopefully as a team we can finish up winning like this. It's a lot better feeling than the middle couple of months, when we were really struggling. I'll think about next year in the offseason. I don't want to cloud my judgment or any visions of the future."

The future looks bright for Hennessey, who has maintained consistency as the closer since the May 31 trade of Armando Benitez. Despite receiving sporadic save opportunities through much of the summer, due to the Giants' poor play, Hennessey entered Tuesday with 12 converted save chances in a row, the National League's second-longest active streak behind Jason Isringhausen's 13 for St. Louis. Hennessey's stretch also was the longest by a Giant since Robb Nen saved 12 consecutive opportunities from June 12-July 28, 2002.

A full-time starter until last season, when he made 22 of 34 appearances for the Giants in relief, Hennessey continues to gain comfort in his adopted role. He has worked on three consecutive days twice in the past five weeks (July 24-26 and Aug. 17-19), reflecting his progress.

"Hopefully I'll get to the point where I can go a bunch of days in a row," Hennessey said. "That'll come with time, but to be able to throw the three or four days in a row is something I never expected to be able to accomplish and feel good while I was doing it."

Rotation shift? Manager Bruce Bochy hinted that the Giants will give additional rest to Tim Lincecum and perhaps other starting pitchers by juggling the rotation and taking advantage of Thursday's scheduled off-day -- their first since July 30.

While emphasizing that Lincecum's arm is sound, Bochy mentioned the possibility of skipping the prized right-hander for a turn or moving him back in the rotation. Lincecum, 23, has pitched 161 1/3 innings this season -- 130 1/3 for the Giants and 31 in Triple-A -- and the Giants are understandably squeamish about pushing him toward the 200-inning level during his first September as a professional.

Bochy didn't divulge specifics, but acknowledged that the expected arrival of Jonathan Sanchez from Triple-A Fresno after rosters expand Saturday could influence plans. Sanchez could provide a break either by being added to the rotation as a sixth starter or providing a spot start. Three more scheduled off-days (Sept. 6, 13 and 27) also offer built-in rest.

Coming up: The Giants and Rockies conclude their three-game series Wednesday at AT&T Park beginning at 12:35 p.m. PT. Left-handers Noah Lowry of San Francisco and Jeff Francis of Colorado will square off.