Complex sentence: In 2003, Garciaparra had a productive season in which he was second in the majors in triples, fifth in the AL in hits, and second in the AL in runs scored, though a September slump caused his batting average to dip to.301.
Split into simpler sentences: In 2003, Garciaparra had a good season in which he was second in the majors in triples, fifth in the AL in hits, and second in the AL in runs scored. Unfortunately, a September slump caused his batting average to dip to.301.