@Gustavo, Co-Moderator posted:
I'd like to hear what David thinks about this.
I think your discussion of the difference is excellent, Gustavo. Like you, I find that the sentence with "a week ago" ("He didn't play tennis week ago") suggests, remarkably, that the speaker didn't even know how to play tennis a week ago:
A: Did you play tennis last week?
B: Are you kidding? A week ago, I didn't even play tennis!