Apparently Shaw won the 3b job on the strength of his defense being better than Panda's. I'm not sure how he compares to Holt, but 3b is probably Holt's weakest position (at least relative to difficulty) and Holt being flexible enough to move around is the thing that makes the whole scheme work.
Both DRS and UZR think Holt is a significantly below-average third baseman. The ML sample sizes for Shaw are too small to mean anything but they have him basically average. I don't know where to find minor league numbers.
I think we might want to break out the bench utilization / pinch hitting issue into a new thread based on Farrell's comments. I'm pretty skeptical of it but feel like it needs a lot of teasing out.
If you look at the scenario from Opening Day, you had Young PH for Shaw (who has the best ML track record against lefties of the three candidates to be PH vs. a LOOGY). Young hits what should be a routine fly out. Next time around, Pablo hits for Young. So you have to look at the benefit of hitting Young for Shaw in a single AB vs. the drop-off from Shaw to Holt/Panda, both defensively and in future ABs against RHP. Depending on how Panda hits, you could end up giving back 100% of the value of Young facing the LHP in the very next PA when Panda is hitting where Shaw would have hit, before you even factor in defense.
Now if you really wanted to get into it you have to factor in the other team's bullpen arms, leverage and game situation, plus positional flexibility for the remainder of the game. I mean god forbid they PH Brock in the 6th inning and then Dustin pulls a hammy in the 7th. Usually when managers are playing the lefty/righty matchups it's with a utility guy still available on the bench, but our utility guy is already in the game, and is in fact one of the people who Farrell might take out of the game to get Young into it.
So if you PH Shaw you are almost certainly downgrading the defense plus risk downgrading that spot in the order for future PAs offensively. When you PH Holt you are one unlucky play away from seeing Pedroia play SS or Shaw play 2B or god knows what. (Ok actually you probably bring Mookie into the infield there, but still). When you PH for JBJ you lose his defense.
There is also the meta-game issue of player usage and development and how this affects the potential ML development of particularly JBJ and Shaw, who both still have a chance to be useful everyday players. It doesn't sound like Farrell is going to be completely trigger happy about this, but to me, if it's a marginal edge, I'm not risking all that positional flexibility and player development just to get Chris Young a few extra ABs.
