San Francisco 49ers' Justin Smith to retire

SAN FRANCISCO, May 18 (UPI) -- The defensive dominoes keep falling in San Francisco, as Pro Bowl defensive tackle Justin Smith retired Monday, according to sources.

Smith, 35, joins a cast of: coach Jim Harbaugh, Patrick Willis, Chris Borland, Frank Gore, Michael Crabtree, and Mike Iupati as 49ers who wont be back next season.

"Justin is the consummate professional whose impact on this organization can never be measured by statistics alone," 49ers general manager Trent Baalke told Yahoo! Sports. "His durability, competitiveness, work ethic, strength and rare stamina helped set him apart over his 14-year career. Cowboy will go down as one of the best to ever wear a 49ers uniform and his candidness, work ethic and pure passion for the game will be missed. We wish the very best for him and his family!"

In his 14-year career, Smith amassed 880 tackles, 87 sacks, 16 forced fumbles, three interceptions and 30 passes defended in 221 games.

"When you're on bald tires, you're on bald tires ... it was just time for me to move on," Smith told NFL.com.