His heart said one thing, but his knees were telling a completely different tale during last weekend's minicamp with San Francisco, and so veteran defensive tackle D'Marco Farr has abruptly ended his comeback attempt and gone back into retirement.

Farr, who hasn't played in an NFL game since 2000 but had hinted several times at a possible return to the field, participated in the Friday and Saturday practices. But he was absent from the Sunday workout, cleaned out his locker stall, and informed coach Dennis Erickson that he was done.

This time, it seems, for good.

Farr last month signed a one-year contract with the 49ers. The deal was worth the veteran minimum base salary of $655,000 and there was no signing bonus. The contract included a waiver that protected San Francisco against any injury that Farr might sustain during his comeback attempt. Thus, the 49ers have no residual effect from Farr's latest decision.

Released by the St. Louis Rams after the 2000 season, and beset by knee problems, Farr acknowledged from the outset he was a longshot to even get to training camp. Niners officials echoed those sentiments.

Although he dropped nearly 20 pounds in the past month, Farr still weighed in at about 299 pounds for the minicamp. His hallmark during a seven-year career with the Rams, in which he played at about 280 pounds, was quickness. In his two days at the minicamp, it was obvious Farr had a long way to go in terms of conditioning, and faced considerable competition even for a backup job.

While the 49ers roster is not deep at the tackle spot, the team did sign veterans Travis Kirschke (Detroit) and Ross Kolodziej (New York Giants) in recent weeks to bolster the position. San Francisco also selected Penn State defensive tackle Anthony Adams in the second round of the draft two weeks ago.

In addition to the physical element involved, Farr was still dealing with the March 2002 death of his three-year-old son, Grant, from a viral infection. In recent years, Farr has said he lost a substantial amount of money in allegedly bad investments with Donald Lukens, a California businessman.

The former University of Washington standout, who made the Rams roster while the club was still in Los Angeles and as an undrafted college free agent in 1994, had worked out in the last two years for a few teams. But the same knee problems that forced St. Louis to cut him after the 2000 season still persisted and thwarted earlier comeback attempts.

Farr was a vital component in the St. Louis victory in Super Bowl XXXIV in 1999. He started 87 games and appeared in 100 contests in his seven seasons with the franchise. Farr had 250 total tackles, 36 ½ sacks, 12 forced fumbles, seven fumble recoveries, three interceptions and 25 pass deflections.

Len Pasquarelli is a senior writer for ESPN.com.