Many can pack the cards that cannot play.

The card-game image contrasts dishonestly arranging the deck with knowing how to play. A person may be able to secure an advantage before the game begins yet still lack the skill needed at the table.

More broadly, the proverb distinguishes scheming to shape the conditions of an undertaking from being capable of carrying it out. Control over the setup should not be mistaken for competence in the work itself.

Use the proverb to question praise for someone who is adept at manoeuvring behind the scenes but unconvincing when it is time to perform. It makes a pointed contrast between gaining an advantage and having the ability to make good use of it.