City won 1-0 to reach the final 10-0 on aggregate with Sandler making his full debut.
Guardiola enthused, "Philippe was very good on the ball and he also did very well in defensive terms.
"We already knew it (his qualities). In the preseason he was injured and needed some match rhythm.
"His dedication is incredible.
"His qualities at the ball ... It was not easy to play well on this field. But he has the insight and in defensive terms he was also very smart. Both central defenders (also the eighteen-year-old Eric Garcia) are so young, but still so good."