Answer:
I'm pretty sure it's because Darry slapped
The direct object is "soccer". It is possible to identify the direct object because it tends to inmediately follow the main verb, which is 'play' in this case. Also, a more effective means of identification is by replacing the word with the pronoun 'something'. Thus, if I paraphrase this sentence it will be: Scott and Maria aplay something. Always remember that a direct object is a syntactic element in a sentence, so it usualñy consists of more than one word, in this case the complete direct object would be: soccer with an old ball they found behind the shell.
