The groove of a player in basketball is the flow and tempo they have when they shoot. If a player gets into a groove, or is grooving, they are consistently shooting accurately and handling the ball well. Synonyms for grooving include "locked in", "heating up", or "on fire".
Players with better poise are more likely to get into a groove, and are also more likely to break out of a slump.
Slumping is the opposite of grooving. If a player is slumping he is shooting the ball poorly, and having trouble handling and moving the ball.
A coach needs to be aware of which of his players are grooving and which are slumping. A coach should always let a player who's grooving ride the wave and stay in the game. If a player is slumping, the coach should bench him for awhile in favor of someone who may heat up.