Firstly, you need to ask yourself if you're actually adding anything to the subject discussed in the other article. Try starting with an acknowledgement of the other post, with a link even, and then discuss why you found it so interesting or what it's made you think about. Expand on some points or disagree with a few and say why. The crux of the matter is, you need to add value to the subject, or at least give an alternative angle.
If you can't do this, consider seriously whether you should tackle the subject at all. If after that, you still just want to cover the same points, then the only thing you can do is to read the blog post you've found and go and look for other posts or articles by different authors on the same subject. Look for at least 5 or 6 others. Each of these will come from a slightly different angle and have slightly different content.
Close all of the articles and go do something else for an hour or two. When you come back, write your own blog post or article on the subject WITHOUT looking at the other articles again. For most people, osmosis will take effect and your article will come out as a mixture of all the articles and it's likely that the reading itself will prompt you to have some original thought of your own somewhere in your own article.