Wells was placed on the disabled list on Wednesday, two days after he experienced numbness in his fingers during a short and ineffective outing in San Francisco.
Wells walked both hitters he faced that night before being removed, and subsequent tests revealed the clot. Prior to that outing, Wells had pitched effectively, and he is 1-1 with a 2.29 ERA in 10 games this season. He started the Rockies' first official game of the season, which came one day after Jeff Francis started the opener that was rained out.
The procedure will be performed by Dr. Rob Thompson at Barnes Jewish Hospital in St. Louis.
"We're very concerned from the physical standpoint of what he will have to deal with,'' Rockies manager Clint Hurdle said. "I spoke with Kip at length yesterday, and with his wife, Emily.
"I told her we're thinking about her as well. This isn't about Kip getting well enough to pitch. This is about Kip getting well. Then we'll take it from there."
The condition isn't new to Wells, as he had surgery on March 6, 2006, to remove a blocked artery in his right arm. At that time, Wells experienced complete blockage of the axillary artery, which is located in the upper chest beneath the clavicle. The artery was replaced with a vein taken from Wells' leg. Wells pitched in only nine Major League games that season. Thompson also performed that surgery.
"They'll revisit the surgery he had a couple years ago,'' Hurdle said. "They feel they have a good idea of how they are going to attack it. But the surgery could be a short one, or it could be a lengthy one. The most important part is for him to get well, and we'll see where it goes from there.''
Wells is 65-92 with a 4.59 ERA in 241 games since his debut in 1999. He signed with the Rockies last offseason and has spent time with the Cardinals, Pirates, Rangers and White Sox.
Cook, currently the Rockies' most effective starting pitcher, missed almost a year after being forced to leave an Aug., 3, 2004, start due to dizziness and shortness of breath. Blood clots were discovered in both lungs, and he subsequently underwent two surgeries before returning in July of 2005.
Tony DeMarco is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.