49ers sign WR Chris Harper

The San Francisco 49ers on Monday added wide receiver help, compliments of the NFC West-rival Seattle Seahawks.

The 49ers signed receiver Chris Harper off Seattle's practice squad, announcing Monday that he had joined the team with a three-year contract.

San Francisco traded linebacker Cam Johnson to the Indianapolis Colts earlier Monday for a conditional 2014 draft pick, creating the open spot on its roster to add Harper.

Harper, who was drafted by Seattle in the fourth round (123rd overall), was among the weekend's surprise cuts.

Seattle then signed him to its practice squad, but San Francisco offered him a chance to join its 53-man roster and he took it.

He finished the preseason with four receptions for 39 yards but dropped two passes, including one on what should have been an easy touchdown reception in Seattle's final preseason game.

The 49ers had five receivers on their roster (Anquan Boldin, Kyle Williams, Jon Baldwin, Quinton Patton and Marlon Moore) after Saturday's deadline to cut to 53 players. Michael Crabtree and Mario Manningham enter the season on the reserve/physically unable to perform list.

Information from ESPN.com's Mike Sando was used in this report.