MLB 14 The Show is available on PlayStation platforms today in the US and tomorrow in Europe through the PS Store, however, the digital release has been delayed on PS4.
You can still download the title for PS3 and Vita or pick up all three versions at retail in the US for $59.99 for PS4 and PS3 or spend $39.99 for the PS Vita version.
Early this morning, some of those who pre-ordered the game on PS4 were experiencing issues downloading the title, as they were supposed to be granted early access to the baseball title at 12.01 am. Sony tweeted that was "aware that some users are unable to download the PS4 game," and was working to resolve the issue "asap."
An update on the US PS Blog, though, notes that "due to unforeseen technical issues," MLB 14 The Show for PS4 is no longer available for download via the PlayStation Store until the issue is fixed.