The four-day-old loss to Chicago continues to hammer away at the Washington Redskins.

As expected, the Redskins placed guard R.C. Thielemann on injured reserve yesterday for a minimum of four weeks and replaced him on the roster with rookie free-agent cornerback Kevin Williams of Iowa State, who was waived by the Redskins Aug. 27 when the team cut its player list from 60 to 50 players.

Williams, who was one of several impressive rookie defensive backs in training camp, is likely to be used on the revamped Redskins special teams.

Thielemann, the former Atlanta all-pro who started his first game for the Redskins at Chicago last Sunday, tore the cruciate ligament in his right knee when his foot became stuck in the artificial turf at Soldier Field, forcing a hyperextension of the knee, head trainer Bubba Tyer said.

Thielemann underwent arthroscopic surgery at Sibley Memorial Hospital yesterday and is expected to begin rehabilitation at Redskin Park soon, Tyer said.

The Redskins had hoped that Thielemann's injury, which occurred while he was wearing a knee brace, might force him to miss only two weeks. "It's a little bit worse than we thought," Tyer said.

Ken Huff, who replaced Thielemann after he was injured in the first quarter Sunday, will regain his starting spot at right guard. The Redskins had wanted to team Russ Grimm and Thielemann, both Pro Bowl players, at the starting guard spots, but now will have to wait until at least Nov. 3 in Atlanta to do that.

Thielemann joins defensive end Steve Hamilton (pinched nerve in his right shoulder), linebacker Monte Coleman (strained right hamstring) and punter Jeff Hayes (partially torn right quadriceps) as players placed on injured reserve after the final 45-man roster was declared Sept. 2.

The Redskins can make four moves off that injured-reserve list this season, plus one move from a preseason injured-reserve list that includes center Jeff Bostic (reconstructive surgery on his right knee).