Justin Smith Farewell Cowboy

San Francisco defensive end Justin Smith (94) and outside linebacker Aldon Smith (99) watch the time wind down as the 49ers trail the Baltimore Ravens during Super Bowl XLVII in 2013 at the Superdome in New Orleans. Paul Kitagaki Jr. pkitagaki@sacbee.com

2015.05.18 – Justin Smith, the iron-clad backbone of the 49ers’ standout defense in recent years, retired Monday, citing a familiar culprit when it comes to ending the careers of 30-something linemen: wear and tear.

“If you don’t have the tools, you can’t do the job,” said Smith, 35. “So it’s time to go.”

Smith follows inside linebackers Patrick Willis and Chris Borland, who retired within a week of each other in March. Smith’s announcement represents another major loss for the 49ers, who went to the playoffs from 2011 through 2013 largely because of the stout play by Smith, Willis and the rest of the defensive front seven.

Unlike Willis and Borland, however, Smith’s decision is not a surprise. And he was decidedly unsentimental about the end of his career.

“You come in, you go out, everything moves on,” the veteran lineman nicknamed “Cowboy” said.

Smith had been leaning toward retirement since the end of the season. He suffered his first major injury, a torn left triceps tendon, late in the 2012 season and had been dealing with injuries, including a bad shoulder, in the subsequent two years.

During training camp in 2013, Smith was going against guard Mike Iupati when something happened to his left shoulder. Seven months later, surgery revealed a piece of bone had detached from the shoulder and became, in Smith’s words, “lodged in the back of it.”

That injury showed why Smith stepped away from the game after 14 seasons and why team officials would have loved to have him back for one more. Despite playing in pain that season, Smith was one of the better defensive linemen in the league, starting all 19 of the 49ers’ games and making the Pro Bowl.

But Smith said Monday the toll on his upper body – especially the left side – had become too much and it was time to call it a career.

“Where I play on the right side, all my contact comes on my left shoulder and left side,” he said. “And it doesn’t respond like I want it to respond anymore.”

Opponents Smith once handled with ease became bigger obstacles in recent seasons, and his production suffered, as did that of the player who lined up next to him, outside linebacker Aldon Smith.

Team officials urged Justin Smith to take his time in reaching a decision, and they likely would have been willing to allow him to practice whenever he wanted in the run-up to the season. Smith, however, said three years ago he didn’t want to be treated as a special case and overstay his welcome.

“As a football coach, you will always be searching for the next Justin Smith, knowing full well you will never find a player quite like him,” said coach Jim Tomsula, Smith’s position coach since 2008. “ … People like to say, ‘They broke the mold with him,’ but there was never a mold. Justin Smith is a handcrafted football player.”

Tomsula and the 49ers have been preparing for Smith’s departure. They used their first-round pick this year on defensive lineman Arik Armstead and have several other youngsters at the position. They also signed veteran free agent Darnell Dockett during the offseason.

With another longtime starter, Ray McDonald, no longer on the roster, the 49ers expect the young defensive linemen to be more involved.

Armstead, Quinton Dial and Tony Jerod-Eddie – all 25 or younger – are in the mix at left defensive end, McDonald’s former spot. McDonald was kicked off the team in December and signed with Chicago in free agency.

On the right side, the plan is for Glenn Dorsey to play on base downs and Tank Carradine to enter in nickel situations. Dockett, still recovering from an ACL injury suffered in August, hasn’t been practicing with the team.

“For four years – you see the D-linemen we’ve brought in – we’ve been making preparations,” Tomsula said in March. “This isn’t a this-year thing for us. We’ve been making preparations. A guy (Smith) gets to 12 years in the National Football League, and he’s about a 92 percent rep count playing defensive line, you better start making preparations. That started awhile ago.”

Smith was the fourth overall pick by Cincinnati in 2001. He mostly was a 4-3 defensive end with the Bengals and had 431/2 sacks in seven seasons with them.

His career took a leap forward when he picked the 49ers over Minnesota in free agency in 2008. He began playing in a 3-4 scheme, bulked up to close to 300 pounds and made five consecutive Pro Bowls (2009-13).

Smith was at his best during the 2011 playoffs when he roughed up Drew Brees and the New Orleans offense in the divisional round. The following week in the NFC Championship Game, he and his defensive mates did the same to Eli Manning and the New York Giants in an overtime loss. Smith played 92.6 percent of the 49ers’ defensive snaps in 2011.

The following year, however, Smith tore his triceps and missed his first starts since his rookie season. He played hurt in most of the games since, and last year, he was in on only 66.7 percent of the snaps.

“I think the one thing that defines him is that he’s just a true warrior in the truest football sense of the word,” former defensive coordinator Vic Fangio said in December. “He played a whole season last year with half an arm. There are a lot of guys that wouldn’t have even gone out there. But the guy loves football, loves playing, loves competing. He’s definitely in my personal top three or five Hall of Fame (players) that I’ve been around.”