PHOENIX -- Chad Tracy experienced a setback recently in his rehabilitation from knee surgery, but the D-backs infielder is hopeful that he will still be ready for Opening Day.

Tracy, who had microfracture surgery on his right knee on Sept. 20, experienced a blood clot in the calf area last week. He is currently taking blood thinners to help alleviate the problem and will stay away from working with the leg for a week or so.

"I think if things go smoothly, Opening Day is possible," Arizona general manager Josh Byrnes said. "If they don't, then it could conceivably drag into the season, but we have been encouraged with the way things went before this little setback."

Tracy traveled to Phoenix the week before Thanksgiving to have his knee looked at by team physician Michael Lee before returning to his home in North Carolina on Nov. 16. He began to experience discomfort in his calf the next night, and it got worse as the week progressed.

"When I got back from Phoenix, my calf started to really bother me," Tracy said. "I didn't think a lot about it because the calf was something that was hurting right after the surgery. But by Thanksgiving it just started aching, so I felt like I needed to get it checked out."

Tracy went to a hospital emergency room Thanksgiving night and an ultrasound revealed the clot.

"The doctors think the flight brought it out," Tracy said. "Some people get clots from flying -- deep vein thrombosis they call it -- and others can get it from surgery. It could have been a combination of the two for me."

The holiday weekend was anxiety filled for Tracy, who was warned by doctors that if he felt any shortness of breath or chest pains that he needed to get back to the hospital immediately. Once he realized that he was OK, though, Tracy relaxed and actually went through an upper-body weightlifting session Tuesday.

"It shouldn't be a big setback," Tracy said. "We've just got to make sure it goes away."

Tracy said the doctors told him the normal course of treatment would be six months on blood thinners, but that if he wants to participate in Spring Training he will likely need to stop taking them before it starts.

Before the setback, Tracy's rehab was seemingly ahead of schedule and he was walking around and had full flexibility in the knee. Tentatively, he won't start running until mid-January, and he has yet to do any squatting.

Judging what is ahead of schedule, though, is tough, because no one gave him an exact timeline. People heal differently, and unexpected things, such as a blood clot, can slow the process.

"You really can't give a timetable," Tracy said. "They said after the surgery that it could be four to eight months, it could be a year. You can't rush something like this."

That kind of uncertainty is tough for Tracy, who likes to map things out in advance and can tell you when he wakes up in the morning what he'll likely be doing each hour for the rest of the day.

"My goal was, and still is, to be ready for Opening Day," he said. "But you just never know. I've been going at rehab pretty hard, and I have to be careful because there's a fine line between working hard and working too hard.

"I mean, we're taking a few days off leg rehab right now, which is something I probably needed to do anyway because I've been going at it pretty hard. It won't hurt to take a week off. In fact, my knee since I've been off it for a few days, feels better than it's felt since the surgery. I feel like I could take off down the street sprinting right now. I'm not going to, but I feel good enough to."