Complex sentence: A product of local CA Osasuna's youth system, Astiz was born in Pamplona, Navarre, and his earlier career was spent with the B-team where he met Jan Urban, a former club player who was manager of the reserves at the time.
Split into simpler sentences: A product of local CA Osasuna's youth system, Astiz was born in Pamplona, Navarre, and his earlier career was played with the B-team. This was where he met manager Jan Urban, a former club player who was manager of the reserves at the time.