Former Super Bowl Champion with the Tampa Bay Buccaneers, Reggie Barlow has played and lined up in every wide receiver position in his career and explains the who usually plays in what role and why.
"Whenever you have two receivers, the slot receiver is just a guy on the inside," he said. "A lot of teams like to use a guy who is a little shiftier and who has a lot of quickness. While a lot of teams to have bigger guys in there, because they can work the middle and take a pounding."
More times than not, the X receiver is the number one wide receiver on the team. He is usually the guy that the team depends on to make big plays. Also, if a team lines up in a formation that calls for only one wide receiver, the one receiver on the football field will be the X receiver.
If the offense shifts into a play where there are two wide receivers split out to either side, they would be called the X and Z receivers.
However, if the formation calls for two receivers and the second receiver is on the same side as the X receiver, then that receiver is considered to be the slot receiver. As its plain to see, the decision on whether or not a second receiver should be called a Z or slot receiver basically depends on where he is lined up on the field.
Now, if there are three receivers on the football field, even if they all are lined up on the same side, the receiver farthest inside would be considered the slot receiver.
According to Barlow, whether or not that wide receiver wants to line up on the line of scrimmage or off the line of scrimmage can be determined by a multitude of factors.
"A lot of coaches have the slot receiver off the line of scrimmage," he said. "But some allow the inside receiver to make the decision whether to be on the line or not."
In most cases, the slot receiver is usually the third best receiver on the team. This is the receiver that comes into the game on long passing downs. However, with the steady advancement in the approach and philosophy of offensive teams attempting to find better ways to get the ball to their top receiver, the number one receiver will sometimes line up in the slot area.
This allows for mismatches for the offense because most times, the best cover guys are always lined up on the outside. So, if you line up your number one receiver in the slot, he may get a one-on-one opportunity with a linebacker or a safety, someone he is obviously quicker than in the open field.
"If it's a 3 receiver set, then he very well could be the third receiver," said Barlow.
