You have shared your concerns about the manager with a co-worker.
At some point after telling him what you think about the manager, your co-worker has started to avoid you, and this has gone on for several days already.
Interpretation #1:
Your co-worker has been too busy with other tasks and feels he can't waste time engaging in conversation with any co-workers (not just you) for the moment.
Interpretation #2:
Your co-worker has reported your concerns to the manager and the manager responded negatively; now he (your co-worker) is afraid of being fired if the manager sees the both of you getting along.
Request for clarification combined with behavior and interpretations:
"Hello there! I haven't heard from you in quite a while; I hope everything is alright. At first I thought you must be so busy these days that you can't afford to drop by and have a conversation, but at the same time, I couldn't help to wonder if this has something to do with the things I told you about the manager last week. Did you speak to the manager about my concerns?"
