Hello.
He sometimes doesn �t play football.
This is correct. The nuance is that he sometimes plays other sports instead.
He doesn �t sometimes play football.
Depending upon the stress put on the words in this sentence, it could be taken as either unnatural or as a response to a statement or question.
For example:
He doesn �t sometimes play football. He always plays football - he is addicted to football.
If a native speaker were to put the stress on those underlined words, the meaning would be understood as a correction. The first person may have said something like "does he sometimes play football" giving no particular stress on any word in the sentence. Then the listener responds as I have tried to show above.
I think this is a matter of pointing out that as a response, your second sentence is OK, but as a regular statement, it is wholly unnatural.
I hope that is a reasonable enough explanation and example for you.
Feel free to respond.
Matthew :)
