Turning running backs taken in the late-rounds of the NFL draft into stars, is the career trademark of Washington Redskins head coach Mike Shanahan.

His latest candidate is Alfred Morris, taken in the sixth-round of this year's draft, from little-known Florida Atlantic. Despite his low draft status, Morris has become an instant hit in D.C.

The rookie is currently fourth in the NFL in rushing, with 491 yards on 100 carries. Like many before him, Morris has certainly benefited from running in Shanahan's famed zone-blocking scheme.

The well-executed scheme has turned more than one unheralded runner into a Pro-Bowler. The first and most famous example is hall of famer Terrell Davis, who took the league by storm as a sixth-round pick for the Denver Broncos in 1995.

After injury ended Davis's career, Shanahan proved that his knack for finding late-round running back talent was no fluke. His zone-based system coaxed 1,000-yard seasons out of Mike Anderson, Olandis Gary, Reuben Droughns and Clinton Portis.

The secret to Shanahan's success is his rigid adherence to the system and how that helps him choose his running backs. When describing an ideal zone back, many pundits will use the phrase "one cut runner."

This is a reference to the single quality that best exploits zone-blocking. That is the ability to instantly recognise a natural cutback lane and make one move or cut to attack it.

By only targeting those runners who have this key attribute, Shanahan has been able to ignore many high-round prospects. If a runner excels at making that one quick cut, Shanahan will select him, even if he doesn't possess top-range speed, elusiveness or power.

It's how a back like Morris can fall to the sixth-round, but become an NFL starter despite playing for a college team that posted a lowly 1-11 finish last season.

Neither Morris or Davis, boasted exceptional speed or agility. However, both backs share one trait that all of Shanahan's best zone-runners have had. That is the ability to make quick reads in the backfield.

It is a mistake often made assuming that zone-runners have to be patient. In reality, the best zone-runners are those who quickly transition what they see into action.

That's because the scheme is good enough to create yards for even a modest NFL rusher. One of the system's signature plays illustrates that boast.

The Redskins often run what is known as the "outside zone stretch play." It is a perfect play for exploiting 4-3 defenses.  It can be run to either side and is keyed by three blockers shifting to the play side in unison. This naturally causes part of the defense to shift with them and splits the front in half.

The Redskins often run the play to the left, either with a tight end or fullback shifting into space with the left side of their offensive line. With three blockers shifting one way, two can attack the defensive end, while the other moves to the second level, to block a linebacker or safety.

On the right side, the center and guard also move up to the linebacker level and take on defenders. From this point, the runner has two options, both devastating for the defense.

His choice is dependent on the action of the defensive end to the side the play is being run. If that end slants inside to try and split the shifting blockers, he gets caught in traffic and presents an easy route around the edge for the runner to exploit.

If the end chooses instead to stay on the edge, he simply creates a bigger cutback lane between the flowing blockers on the left and those moving forward on the right. It's easy to see why speed of thought is the essential attribute for a zone-back, who must quickly identify and choose which lane to attack.

It also explains why Shanahan features lighter offensive linemen. Mobility is key for zone-blockers who must make their initial block and quickly move into space to block linebackers and defensive backs.

Their ability to take out defenders at the second level, is why many runners in the zone scheme gain seven or eight yards before the first defender hits them.

This stretch play has defined Shanahan's history of turning unheralded runners into Pro-Bowlers. As the 4-3 is still the vogue defense in the NFL, Shanahan has mastered the art of exploiting its biggest weakness, the edges.

Morris has gained all of his yards against 4-3 defenses so far this season. He topped 100 yards against both the Tampa Bay Buccaneers and Atlanta Falcons.

In all, the Redskins have seven more games against 4-3 teams, so Morris has a great chance to become Shanahan's next Pro Bowl running back.