Sentence:  Before kick-off, a section of Chelsea's support <WSD>sadly</WSD> let themselves and their club down by noisily interrupting the silence held in memory of the Hillsborough disaster and for Livorno midfielder Piermario Morosini, who collapsed and died after suffering a heart attack during a Serie B game on Saturday. 
Meaning of the word marked with <WSD> tags:  Unfortunately, sad to say.