Again, teams have not schooled their players WHEN to challenge. If it's a 3-2 count in that situation, sure, keep the inning going (if you're right). A challenge can NEVER be on a pitch count other than a 3 ball count (unless it's an overly obvious missed call by the ump).
I understand resting guys, but rest Walker in the As game, not contending teams like Seattle, plus when Pena got hurt, bring Walker as the bat substitute and move Correa to ss, Paredes to 3rd. Would hate missing playoffs by one game again.