If you ever get confused whether you should use 'who' or 'whom', try using the pronoun 'he' this way: I have a friend HE plays soccer. If you can substitute 'who/whom' with 'him' and then it's 'whom', otherwise it's 'who'.

The first option is correct. "whom" is used when the person is the object of the sentence. For example, "It's the person with whom I play soccer." "whom" is formal and is used in writing. In daily conversations we use "who". Here we also can say "I have a friend that plays soccer."