Peterson celebrated his 32nd birthday two weeks ago, and missed most of last season due to a right knee injury, the second time in three years he has missed significant time due to a knee injury (he tore his ACL in 2014). But in 2015, Peterson bounced back from the ACL tear by leading the league in rushing yards (1,485) and rushing touchdowns (11).
Peterson has played in just five playoff games in his career. Signing with the Patriots would almost certainly mean that number would increase.
Peterson likely isn’t viewed as a workhorse anymore, but the Patriots don’t really do workhorse backs; the last New England running back to average 20 carries a game over a season was Corey Dillon in 2004. LeGarrette Blount had 299 carries last season, but averaged just 3.88 yards per attempt. Blount is a free agent.
The Vikings have left the door open for Peterson to return to Minnesota, although they signed running back Latavius Murray this offseason.