What video card do you currently have? what type of internet connection do you have? how much ram does your computer have? You may want to post some of this info in your profile when you say the video looks bad is it choppy? is there any way you could post a screenshot of what it looks like?
If it was me I would say it might be the feed coming from MLB.TV You might want to check out their F.A.Q. section on their website to see if others are having this problem.
After you post some of your system specs maybe we can determine if it is best to upgrade.