When middle linebacker Sam Cowart suffered a partially torn Achilles tendon in the season opener, Buffalo Bills coach Gregg Williams acknowledged the team's defensive star likely would miss a "significant" amount of time.

	Cowart

It appears now that "significant" translates into the balance of the season.

After deliberating several options, and consulting with a number of experts, Cowart underwent surgery Friday to repair the tear. The operation was performed by Dr. John Marzo, the Bills' team physician.

The team will hold off placing Cowart on injured reserve, which by definition would mean he could not return until next season. Still, the Bills appear resigned to playing the rest of this year without him. Once the results of the surgery are clear, it's very likely Cowart will go onto the injured reserve list.

General manager Tom Donahoe termed it a "long shot" Cowart could get back on the field this year and Williams said the surgery was more a factor of repairing the linebacker for the future.

The injury occurred as Cowart was backing into pass coverage early in the game last weekend.

A fourth-year veteran and the spiritual leader of the defense, Cowart will be replaced in the lineup by Kenyatta Wright, a second-year pro who started one game during his 2000 rookie season. Rookie Brandon Spoon, a fourth-round choice from North Carolina whom the Buffalo coaches really like, probably will get more playing time as well.

"All you can do," Wright said, "is play your best. No one can replace Sam, but this is an opportunity for me to do some things."

Cowart, 26, was named to his first Pro Bowl berth in 2000 despite missing the final four games of the season with an ankle injury. Even though he played just three-quarters of the season, Cowart rated among the NFL's leading tacklers, with 181 stops. The former Florida State star was a second-round draft choice in 1998 and earned a starting spot early in his rookie season.

Len Pasquarelli is a senior NFL writer for ESPN.com.