This is a straight forward achievement, but there are two things to note about it that might not be apparent:
1. You have to get all 4+ rushing touchdowns with the same player. (I got 5 rushing touchdowns with Green Bay in one game, but the achievement did not pop because I had gotten the TD's with 4 different players - and no single player had 4 TD's.)
2. You can do this with any position (RB, QB, WR) - it doesn't necessarily have to be a RB. (I got this particular achievement while also working on the QB rushing achievements.)
Figured I'd make those two notes, since the achievement description is a little vague, & it hadn't been noted anywhere else on TA that you needed to get all the TD's with one individual player.