Do baseball players use the on deck circle?
Baseball players do use the on-deck circle and they use it to prepare for their at-bat. Some players just stand there and do nothing, but this is not the purpose.
The semi circle at the edge of the 18yrd box is there to keep the players 10yrds away from the ball during a penalty kick. No players are allowed in the semi circle until the ball is kicked during the penalty. During normal play the semi circle offers no use. It is not part of the box so the goal keeper will commit a foul if handeling the ball in the semi circle.