Sapiyev took control of the contest in the first round and had built up a four-point cushion by the bell.
Maestre responded well and drove forward in the second, forcing a standing count on his opponent.
That woke the Kazakh up and he regained the initiative as the round came to a close.
Sapiyev boxed cleverly in the final round as he stayed out of range, while throwing single scoring shots to keep adding points to his tally.
In the end, the Kazakh ran out a 20-9 winner.