I believe there is a Spring Training competition index that tells you what type of competition players have been facing during the course of ST. I think it is on Baseball Reference under the spring training stats for any particular ball club. http://www.baseball-reference.com/teams/BOS/2016.shtml
So Shaw has an OppQual of 8.1, meaning that he has been facing generally competition that is of AAA quality. Out of all your starters Kelly has faced the weakest opponents besides Owens, at 8.4. So he is right around the AAA quality competition as well, but then again so is Price at 8.6
I know this doesn't take into account players working on different things like bunting or throwing a certain pitch, but it does help to quantify who a person is playing against.