Complex sentence: Jim McLean's playing debut for Dundee came in the city derby at Dens Park on September 11,1965 when Dundee suffered their heaviest ever defeat (5-0) to rivals Dundee United.
Split into simpler sentences: Jim McLean's playing debut for Dundee came in the city derby at Dens Park on September 11,1965. A match in which Dundee suffered their heaviest ever defeat (5-0) to their rivals, Dundee United.