Justin Smith has revealed that a shoulder injury played a huge part in his decision to retire from the NFL after 14 seasons.
The San Francisco 49ers defensive tackle sustained a shoulder injury during training camp ahead of the 2013 season, but he played through the pain barrier to feature in all 18 of his side's matches.
However, off-season surgery revealed that he had broken a bone in his shoulder, which could not be repaired by the procedure.
Smith still played at a high level in the 2014 campaign, but has now conceded that time has caught up with him.
He told reporters: "When you get on the bald tires, you're on the bald tires. It just never bounced back. It's just one of those things. I'm just lucky and fortunate it happened year 13 and 14, not year two.
"Where I play on the right side, all my contact comes on my left shoulder and left side. And it doesn't respond the way I want it to respond anymore. If you don't have the tools, you can't do the job. So it's just time to go.
"Obviously you want everything to work the way you want it, but nobody is going to moan about getting hurt playing football. It's a young man's game. As you get older, it's harder to get that same intensity going week in and week out. It was just time for me to move on."
Smith recorded 880 tackles, 87 sacks and three interceptions in his 14-year career with the 49ers and Cincinnati Bengals.
