Complex sentence: Gant had an average rookie season, but wouldn't get to play every day until two years later, in 1990, when he batted.303 with 32 home runs and 84 RBI's.
Split into simpler sentences: Gant had an average rookie season, but wouldn't get to play every day until two years later, in 1990. That year, he batted.303 with 32 home runs and 84 RBI's.