Complex sentence: Dean Hopkins started off his junior career with the 1974--75 Owen Sound Greys of the Mid-Ontario Junior B Hockey League, moving on to the Ontario Hockey League's London Knights from 1975 until 1979.
Split into simpler sentences: Dean Hopkins started off his junior career with the 1974--75 Owen Sound Greys of the Mid-Ontario Junior B Hockey League. Afterwards played with the Ontario Hockey League's London Knights from 1975 until 1979.