Unfortunately, that doesn't do anything to predict how he will perform with the Mets.
Bobby Mueller of FanGraphs put up a pretty dorky (in a good way) story about pinch-hitters today. Although we rarely talk about bench bats when analyzing the strengths and weaknesses of baseball teams, there were squads last season that were hurt or helped in a material way by their pinch-hitters.
Despite being in the American League, the Orioles were tied for tops in the majors with 0.7 fWAR from pinch-hitters. That was with much thanks to Delmon Young, who raked .313/.395/.522 as a substitute in 2014. Even better than that was current Met John Mayberry Jr., who hit .400/.438/.933 in 32 pinch-hit plate appearances between Philadelphia and Toronto. Although Mayberry was only worth 0.2 fWAR total last year, he was worth 0.8 fWAR as a pinch-hitter.
That's the good news. The bad news is that pinch-hitting performance can vary wildly from year to year, even when highly experienced bench bats are involved. Just look at perrenial Mets-killer Greg Dobbs, who raked as a pinch-hitter from 2006 to 2008 before falling off a cliff for two seasons and finally resurfacing in 2011 as a valuable weapon. After that, it was back on the struggle bus for Dobbs, who was lousy in 2012 and 2013 before bottoming out last season as one of the most abysmal pinch-hitters in the majors.
Mayberry's story is similar. He was a very good pinch-hitter for his first two seasons in the league before struggling for three seasons and finally breaking out in 2014. As a position player last year, Mayberry was pretty lousy, but he did hit .214/.353/.500 in right field, where he'll probably see most of his at-bats with the Mets in 2015.
Small sample sizes are everywhere in this analysis, but Mayberry appears to be someone who can provide a nice punch against lefties off the bench. If all goes well, he could even be worth a whole win, which could make all the difference in the race for the postseason.