I have a Wordpress website on which I'm using Yoast SEO plugin. This plugin states that on a single post I have to target only one focus keyword for better SEO PageRank.
Now suppose I have two related keywords like baseball bat and bats for baseball and I want to target both so I have to create two post. One targeting baseball bat and another bats for baseball and optimize of there respective keywords. This is easy.
But how these post are going to show in my navigation? If I give link to both they are after all saying about same thing, with little difference. so its look to me like I'm spamming and what user is going to get benefit from this.
But my competitors are doing this shamelessly and getting traffic.
One other possible way is that in navigation show only one main post like show baseball bat in main navigation. Other versions of post for different targeting keyword like bats for baseball let it be there and indexed and optimized but not showing in main navigation.
Guide me if you understand what I'm trying to say.
You thinking too much into it, "baseball bat" and "bats for baseball" are quite clearly synonymous terms so you can happily use them on the same page and target the page for both terms.
The focus keyword here for the Yoast plugin would be 'Baseball bat'.
If you start making posts for every keyword veriation you can think for baseball bats, you website will soon look very spammy.
As Google always says, create site for users, not search engines.
For this you have go for the paid service. You will be able to add 5 Keywords.