When Justin Smith decided that his body wouldn't let him perform up to his own lofty standards, he knew it was time to stop playing.
Smith, who starred for the Jefferson City Jays and Missouri Tigers, announced Monday he is retiring after 14 seasons as one of the top defensive linemen in the NFL, dealing yet another blow to the San Francisco 49ers in a rough offseason.
"They all want you to keep playing, and I want to keep playing as well, but when you get on the bald tires, you're on the bald tires," Smith said.
One of the most durable players at one of the most physically demanding positions, Smith had been hampered the past two seasons by an injured left shoulder that he first hurt in training camp in 2013.
That shoulder absorbed the brunt of the punishment as a right defensive end going up against 300-pound linemen all game and Smith did not feel up to playing another season.
"It doesn't respond like I want it to respond anymore," he said. "If you don't have the tools, you can't do the job. It's time to go."
While Smith could still be an effective player, he could no longer be the dominant one he had been for so long in his career and that's what led to his decision.
"People are going to compare him to everybody else," 49ers coach Jim Tomsula said. "Justin Smith doesn't compare himself to anybody else. He compares himself to himself. That's the bar he sets. ... I've always known with Justin that if he didn't feel like health-wise he can play at the level he plays at, he's not going to do it."
Smith had just two sacks in the final 14 games last season as his practice time, snap count and effectiveness dwindled toward the end of the season.
Smith is the third defensive star to retire from the 49ers this offseason, joining linebackers Patrick Willis and Chris Borland. Coach Jim Harbaugh is also gone, along with running back Frank Gore, guard Mike Iupati, receiver Michael Crabtree, linebacker Dan Skuta and cornerbacks Chris Culliver and Perrish Cox.
Smith played 14 seasons in the NFL after being drafted in the first round by Cincinnati in 2001. After seven successful seasons with the Bengals, he signed as a free agent in San Francisco and had his best success in seven years with the 49ers.
Smith was the anchor of San Francisco's 3-4 defense that made three straight trips to the NFC title game from 2011-13 and one Super Bowl appearance. He tied up blockers and broke down protection to help the team's stellar linebacker corps of Willis, Navorro Bowman and Aldon Smith succeed.
While Justin Smith never recorded double-digit sacks in a season in his career, he was so well-regarded he was selected as an All Pro first-team defensive tackle and second-team defensive end in 2011. He was the first player ever to make the AP's first and second team at different positions.
"Justin is the consummate professional whose impact on this organization can never be measured by statistics alone," 49ers general manager Trent Baalke said. "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."
Justin Smith also was picked as a second-team All Pro defensive end and defensive tackle in 2012 and made five Pro Bowls in his seven seasons in San Francisco.
At Jefferson City, Justin Smith's high school career came to a close with the Jays' 10th state title. That year, he had 124 tackles, 15 sacks, four forced fumbles and two recoveries. The Holts Summit native also played tight end for the Jays and hauled in 15 passes for 270 yards and five touchdowns his senior season. He earned all-state honors two years and was twice named all-district.
At Missouri, Justin Smith was named Big 12 Conference defensive newcomer of the year by the Associated Press in 1998 when he was the first true freshman to start every game for the Tigers since 1986. He was named a defensive first-team all-American as a junior in 2000 and was all-Big 12. He recorded 11 sacks that year to set a school record, which stood until future San Francisco teammate Aldon Smith recorded 11.5 in 2009. Justin Smith still holds the Missouri record for tackles for loss in a season with 24 in 2000 and in a career with 50. His four sacks against Baylor on Nov. 11, 2000 tied a school record that still stands. His 22.5 career sacks are tied for second most at Missouri.
Smith departed after his junior year and was drafted fourth overall by the Bengals in 2001, tied for the earliest a Missouri Tiger has ever been selected (Russ Washington, 1968).
During his NFL career, Smith started 217 of 221 games played, including a streak of 185 consecutive starts from his rookie season through December 2012. He finished his career with 1,370 tackles, 87 sacks, 16 forced fumbles, 10 fumble recoveries, three interceptions and 30 passes defensed.
Smith posted at least five sacks in 12 of his 14 seasons played and is one of 13 players to register five or more sacks in at least 12 seasons since sacks became an official statistic in 1982.
"Whether it was chasing down a wide receiver and forcing a fumble to seal a win, or driving a tackle back into the quarterback's chest, he gave everything he had every play," 49ers CEO Jed York said. "Justin has earned the respect of the entire NFL community and he will always be remembered as one of the 49ers all-time greats."