Shawne Merriman's retirement, announced on Tuesday, summons a variety of photos from the mind's scrapbook: locomotive No. 56 steaming into offensive backfields; talent-rich Chargers teams that dazzled yet never reached a Super Bowl; Merriman fading well before his 28th birthday, derailed by a severe knee injury and stigmatized by a failed drug test.

Drafted in 2005 by the Chargers, who chose him 12th out of Maryland, the outside linebacker reached the Pro Bowl in each of his first three seasons.

In that span, he amassed 39.5 sacks, including an NFL-best 17 in 2006.

There wasn't a more talented NFL team from 2006-07 than the Chargers, and Merriman, 6-foot-4, 270 pounds, gave them an additional edge.

“He helped change the attitude on that team,” Jim Trotter, an NFL writer for Sports Illustrated, told me on Tuesday. “It was no longer about allowing other teams to dictate terms. They were going to come after you, and Shawne was the guy who helped initiate it, along with Steve Foley (a teammate in 2005).”

Merriman could’ve become a Hall of Fame candidate had he continued to run past and over blockers.

But a knee injury limited him to one game in 2008. A year later, he had only four sacks, although he set the edge for a Chargers team that went 13-3.