Rayburn, 26, will sign a one-year contract that includes a modest signing bonus, a base salary of $595,000 and incentives based on playing time and sacks. He had also visited with the Buffalo Bills and had drawn interest from several other clubs after his release.
Primarily a 4-3 tackle in Philadelphia, Rayburn is projected as a left end in the 3-4 front used by the 49ers. He will back up 13-year veteran Bryant Young, be a key part of the end rotation and will likely see considerable playing time in passing situations.
The deal with San Francisco affords Rayburn several advantages. It will permit him to showcase his skills in a 3-4 for the first time, which will give him some versatility and will provide him an opportunity to re-establish himself in the league. And barring an extension, Rayburn will go into the unrestricted market next spring.
The subject of trade rumors the past several offseasons, Rayburn was released when he became the odd man out on a Philadelphia roster with a rare surplus at defensive tackle. Not many teams enjoy the kind of depth at tackle that the Eagles have, with five solid tackles, and team officials tried to trade Rayburn before releasing him.
A former Tulsa standout, Rayburn, 26, earned a spot on the Eagles' roster as an undrafted college free agent in 2003. In four seasons, he notched 98 tackles, nine sacks, two forced fumbles, one recovery and one pass defensed in 52 games, including four starts.
His best season was in 2004, when Rayburn had 46 tackles and six sacks, despite playing mostly in a backup role.
Rayburn had five years remaining on his contract in Philadelphia at the time of his release.
Len Pasquarelli is a senior NFL writer for ESPN.com.