Madden NFL 08

This is very easy to do with two controllers. Set sliders to your favor first (turn yours all up, CPU all down). Put the quarters time to 1 minute, turn all rules as well as fatigue and injuries off.

You play Patriots against Raiders. Have the Raiders kick off, so you get into possession right away. As your play, select HB Stretch (which is a Run play). As opponent's play, select FG Block (which is under special team). That way, your right and left side are completely devoid of any opponent players. After pressing A, your players will trade the ball and you just need to run as quick as possible with the ball through the right (or left) side towards the goal. Usually, that's a ~50yard rush, so even if you fail the first time, you can still have an yard average of 24 if you succeed on the second rush.

Check your stats after doing a successful rush - if it says 20.0 or more for one player on average, just don't do any rush plays anymore, and don't simulate the game either. Just let the clock run out (by "taking a knee", which means you use the play "QB Kneel") and you're set.

For this achievement you need to average 20 yards a rush, which means if you take your total rushing yards and divide by attempts, it needs to equal 20 or more. I'm pretty sure this stat is listed in the deluge of stats that is the stats page.

Regardless, the easiest way to do this is just rush once for 20+ yards (I find toss plays to the right to be good for this) and then pass the rest of the game. Obviously set the game length to the smallest, and you can set the difficulty to rookie but it's not all that necessary.