-- Star right tackle Jon Jansen suffered a ruptured left Achilles' tendon on the Washington Redskins' second possession of the preseason in the Hall of Fame Game Monday night against the Denver Broncos at Fawcett Stadium in Canton, Ohio.

Jansen went down in the first quarter on a passing play to the far side of the field and could not get up. He received immediate medical attention, had to be helped to a bench on the sideline and was carted out of the stadium several minutes later with what could be a season-ending injury; team officials would not comment on the length of Jansen's absence until more testing was concluded.

Jansen, the longest-serving member of the team, is an integral part of Washington's rebuilding hopes under Hall of Fame coach Joe Gibbs, and losing him for any significant amount of time would be a severe blow. Jansen and the entire offensive line were criticized heavily last season under pass-happy coach Steve Spurrier, and the return of assistant head coach-offense Joe Bugel had renewed optimism that the unit would improve in a run-oriented offense.

As a right tackle, Jansen protects the blind side of left-handed quarterback Mark Brunell, the starter in the exhibition opener, and replacing someone of his caliber at this stage of the preseason would be quite difficult.

It was clear right away that Jansen was suffering. Quarterback Patrick Ramsey, his close friend, came over to the bench twice to console the tackle. Jansen grimaced and put his hands in his face before the training staff draped a towel over his head. Bugel also attended to the injured player and owner Daniel Snyder was quickly on the phone to team officials seeking an update on the situation. Daryl Terrell, a seven-year veteran who was signed as a free agent in 2003, replaced Jansen for Washington's next series.

Jansen, who is 6 feet 6 and 305 pounds, was selected 37th overall in the 1999 draft from Michigan and had been one of the most durable players in the NFL, starting 82 straight games. He regularly faces some of the most feared pass rushers in the league and, despite not appearing in a Pro Bowl, is considered one of the elite linemen in the game.

Gibbs, back to coaching after an 11-year absence, was counting on Jansen and bookend tackle Chris Samuels to make the offensive line one of the team's strengths this season, particularly after the acquisition of explosive running back Clinton Portis from Denver. Jansen is a student of the game who grew up idolizing "the Hogs" of Washington's glory years and was enthused to work with Bugel, who coached that group to greatness.

Right tackle Jon Jansen, the longest-tenured Redskin and a key to the offensive line, awaits medical attention after tearing his left Achilles' tendon in the first quarter against the Denver Broncos.