protected function pushEmptyGroupsToTree($numFighters)
    {
        if ($this->championship->hasPreliminary()) {
            /* Should add * prelimWinner but it add complexity about parent / children in tree
            */
            $numFightersElim = $numFighters / $this->settings->preliminaryGroupSize * 2;
            // We calculate how much rounds we will have
            $numRounds = intval(log($numFightersElim, 2)); // 3 rounds, but begining from round 2 ( ie => 4)
            return $this->pushGroups($numRounds, $numFightersElim);
        }
        // We calculate how much rounds we will have
        $numRounds = $this->getNumRounds($numFighters);

        return $this->pushGroups($numRounds, $numFighters);
    }