Complex sentence: They went into the final day of the season a point behind Derby County, who had already finished their campaign, but were unable to secure the victory they needed against Arsenal to win the League, finishing in third place.
Split into simpler sentences: They went into the final day of the season a point behind Derby County, who had already finished their campaign. However, they were unable to secure the victory they needed against Arsenal to win the League and finished the season in third place.