The most combined net yards gained by a single player in an NFL season is 2,969, by Darren Sproles, playing for the New Orleans Saints (both USA) in the 2011 season.
Sproles had 40 yards rushing, 29 yards receiving and 99 yards on kickoff and punt returns to finish the season with an NFL record 2,969 combined yards, easily breaking the previous mark of 2,690, set by Derrick Mason, playing for the Tennessee Titans (both USA) in 2000.