Complex sentence: They were unable to overhaul the lead Chelsea had, and finished the season in second place, which is their highest ranking in 54 years since the 1962/1963 season under Bill Nicholson, as well as their first unbeaten home run in 52 years since the 1964/65 season.
Split into simpler sentences: They were unable to overhaul Chelsea's lead in the league table, and finished the season in second place. This is their highest ranking in 54 years since the 1962/1963 season under Bill Nicholson, also achieving their first unbeaten home run in 52 years since the 1964/65 season.