The phrase "to keep the player" means to make sure that a person remains engaged, interested, or loyal to a certain activity, game, or situation. Full definition
A physical therapist lists the warning signs of a potentially serious back problem and offers tips for keeping players on the court and back - pain free. (MomsTeam.com)
Also, we saw that we could work more on the level design for keeping the players engaged for longer. (gamesauce.biz)