The debate over open- versus closed-stance groundstrokes has raged for more than a decade. Now that the dust has settled, experts agree that players have an advantage when they're able to use all variations and stances depending on the situation.
A player's ability to develop both an open and closed stance begins with footwork. The traditional closed stance forehand is struck after a player's non-dominant, or lead, foot has stepped toward the net. If the player were standing on a clock face, the back foot would be at 6 o'clock, and the front foot would positioned at nearly 12 o'clock. The player's feet are almost perpendicular to the net. For a closed-stance backhand, the feet are reversed.
The closed-stance forehand should not be confused with a crossover-step forehand, an emergency stance in which the front foot crosses completely in front of the body and points towards the side fence. This footwork locks the hips which inhibits core rotation and can cause balance issues. The stance should only be used in extreme defensive situations when the player is on a dead run and has zero time to apply a more desirable setup.
The open-stance forehand is struck after the player steps to the side to line up the incoming ball with the dominant leg. to use the clock analogy again, for a right-hander, the dominant foot is standing on 3 o'clock, and the non-dominant foot is around 9 o'clock (reverse positions for a lefty). In this stance, the player's feet are nearly parallel to the net. For an open-stance backhand, a player will line up the incoming ball with the non-dominant leg.