49ers release cornerback Shawntae Spencer

SANTA CLARA, Calif. (AP) - Shawntae Spencer became the odd man out in San Francisco's secondary.

The 49ers released the cornerback Thursday after he spent eight seasons with the team. Later in the day, the 49ers agreed to terms on a one-year deal with free agent special teams standout and backup running back Rock Cartwright, a person with knowledge of the negotiations told The Associated Press. The person spoke on condition of anonymity because the team had yet to make a formal announcement of his signing. Cartwright, who played the past two seasons with the Oakland Raiders, should help fill a void after Blake Costanzo signed a two-year contract with the Chicago Bears on Tuesday.

Also Thursday, free agent wide receiver Mario Manningham and former 49ers wideout Brandon Lloyd visited team headquarters, another person with knowledge of the meeting confirmed to the AP, speaking on condition of anonymity because it wasn't made public. Chaz Schilens met with the team Wednesday.

Manningham caught a 17-yard touchdown pass from Eli Manning with 8:34 remaining in regulation of the eventual Super Bowl champion New York Giants' 20-17 overtime win over San Francisco in the NFC championship game Jan. 22 at Candlestick Park.

The 25-year-old Manningham had 39 catches for 523 yards and four touchdowns last year in his fourth NFL season. Lloyd, who played three seasons for San Francisco from 2003-05, made 70 receptions for 966 yards and five touchdowns in 11 games for St. Louis last season.

If the 49ers add another top-tier wideout, they would have quite the dynamic receiving corps after signing Randy Moss on Monday to join Michael Crabtree and tight end Vernon Davis.

Quarterback Alex Smith is expected to re-sign soon with the 49ers and has said he is weighing a three-year contract offer.

The 30-year-old Spencer started every game in 2009 and 2010 but appeared in only nine games with no starts for coach Jim Harbaugh and the NFC West champions last season.

On Tuesday, the 49ers signed cornerback Perrish Cox. They also have agreed on a new $31.3 million, four-year contract with Pro Bowl cornerback Carlos Rogers.

San Francisco selected Spencer in the second round of the 2004 draft, out of Pittsburgh. He has 345 career tackles, 11 interceptions, three forced fumbles and a touchdown in eight NFL seasons.

Schilens had 23 catches for 271 yards and two TDs last year with the Oakland Raiders.