Brown was nursing an undisclosed injury for the past few weeks and was unable to work his way into a crowded backfield after signing with New England on March 17.
"He hasn't been available for a while," coach Bill Belichick said. "Yeah, it's unfortunate. He worked hard; he's a really good kid. We just never really got the chance to see him."
The 29-year-old Brown has rushed for 2,829 yards and 18 touchdowns and reeled in 120 receptions for 1,066 yards and two scores in 89 games since being selected by Indianapolis with the 27th overall pick of the 2009 draft.
Brown finished with just 229 yards rushing and one touchdown in 10 games with San Diego last season.
Biggers, who was signed as an unrestricted free agent from Philadelphia on March 30, recorded 44 tackles and seven passes defensed in 16 games with the Eagles last season. The 29-year-old has played for Tampa Bay, Washington and Philadelphia in his career since being selected with a seventh-round pick in the 2009 draft.
Kearse, 27, has also played for three teams during his career, recording 43 tackles, 5 1/2 sacks and one pass defensed in 35 games with Carolina, Dallas and Washington.