SB 10.18.19

tatropāhūya gopālān
 kṛṣṇaḥ prāha vihāra-vit
he gopā vihariṣyāmo
 dvandvī-bhūya yathā-yatham
Synonyms: 
tatra — thereupon; upāhūya — calling; gopālān — the cowherd boys; kṛṣṇaḥ — Lord Kṛṣṇa; prāha — spoke; vihāra-vit — the knower of all sports and games; he gopāḥ — O cowherd boys; vihariṣyāmaḥ — let us play; dvandvī-bhūya — dividing into two groups; yathā-yatham — suitably.
Translation: 
Kṛṣṇa, who knows all sports and games, then called together the cowherd boys and spoke as follows: “Hey cowherd boys! Let’s play now! We’ll divide ourselves into two even teams.”
Purport: 

The word yathā-yatham means that Kṛṣṇa naturally wanted the two teams to be evenly matched so that there would be a good game. In addition to the pleasure of sporting, the purpose of the game was to kill the demon Pralamba.