There's some talk lately about free agent running back Chris Johnson signing with the Dallas Cowboys. It's an exciting idea for fantasy owners: the Cowboys have the league's best offensive line and nearly produced a 2,000-yard rusher last year, while Johnson rushed for 2,000 yards back in 2009.

But while Johnson is just 29 years old and might figure to have at least another good season in him, there's evidence that he's nowhere near the same player he was back then. Specifically, take a look at his explosive plays, or lack thereof, in the years since his biggest season.

Back in 2009, Johnson had a whopping 22 runs of at least 20 yards and 7 runs of at least 40 yards. In the last five seasons, in contrast, only once has he had more than half that many big plays. Last year Johnson split carries while with the Jets, but his big plays had been steadily dwindling for several years before that.

Johnson's 20- and 40-yard runs in his career are presented below.

CHRIS JOHNSON'S BIG RUNS, 2009-2014
Year Team Att Yds 20+ 40+
2009Titans 3582,006227
2010Titans 3161,364134
2011Titans 2621,047111
2012Titans 2761,24383
2013Titans 2791,07750
2014Jets 15566341

--Andy Richardson