The secondary line of defense in volleyball are the 1. server,
2. backline players,
3. frontline players,
4. spiker

2) Backline Players

Explanation:

There are six players on court in a Volleyball team, who each must rotate one position clockwise every time their team wins back service from the opposition. Only the three players at the net positions can jump and spike or block near the net. The backcourt players can only hit the ball over the net if they jump from behind the attack line, also known as the three-metre line, which separates the front and back part of the court.

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Frontline players.

Explanation: In order, it's the spiker, the frontline players, the server, and the back line players. The backline players are obviously in the back, and the spiker needs to be in the way front in order to spike it down over the net. The secondary line of defense are the frontline players, who are obviously in the front, hence the name, although not as far front as the spiker. After that is the server, who needs to be nearer to the back, but not all the way in the back.