For a first time shooting tennis you got a nice serie, but they are not super.
You want the player & action to be sharp and standing out from the background. This means you have to shoot wide open or as wide as is required to get sharp results from your lens. I think the DA*200 will already give sharp results at F2.8, but may get the best results at F4-F5.6. You will then also easily see where your focus point has been in the shot. As far as I see your pictures most of the time focus on something in the background (linesman).
For tennis you also want to freeze the action using a very short shutterspeed, preferably 1/750-1/1500. You can see motionblur in #10, 1/400 is too slow.
For sports I therfor often use TAv since I can select both shutterspeed and aperture. With the K5 you don't have to worry too much about high ISO noise and given the sunny circumstances you had that should be no problem at all.
You already got info about AF. You could try AF-C and single focus point and look at the results.
Hope this helps to get even better shots next time.
Here some tennis shots I took last year.
https://www.pentaxforums.com/forums/post-your-photos/104875-sports-tennis-uni...smalen-nl.html