Matt Joyce has played in nearly 300 major league games spanning over parts of 4 season (2008-2011) and has over 1000 plate appearances to his credit. As a left handed batter he has been sheltered from having to face left handed pitching as evidenced by his 874 career plate appearances (86% of all plate appearances) versus right handed pitching while garnering only 142 plate appearances versus left handed pitching.
The reason to sit Joyce against LHP becomes clear when looking at his career splits. Against RHP he has a OPS of .867 (.270/.355/.512 with a wOBA of .369) while struggling versus LHP posting an OPS of .608 (.190/.275/.333 with a wOBA of .273). As shown in the table below, Joyce is getting his first real opportunity to prove that he can't hit LHP as he has been given 81 PAs in 118 games while he only had 60 PA in the previous three seasons combined over 180 games.
Matt Joyce got off to a blazing start of the 2011 season and then struggled either due to a shoulder injury, a natural regression, or a combination of both. Joyce has rebounded from the disappointing June and July to post a very nice August by hitting a .787 OPS (.282/.364/.423).
When looking over Joyce's month-by-month performance the question that kept percolating in my mind was whether or not Joyce's performance against pitcher handedness changed as well? In other words, when Joyce performs well against RHP does he also perform well against LHP and does the same hold true when he struggles against RHP (does he struggle against LHP as well)? The month-by-month splits for Matt Joyce are presented after the break.
As shown in the tables below, Joyce has been given approximately the same amount of plate appearances for each month of the 2011 season. I will proceed forward with the understanding that less than 20 PA per month isn't a statistically significant sample size as the data is being presented for discussion more than it is to prove or disprove a theory. I'll be looking at the difference in OPS against LHP and RHP more than the individual components of the slash line.
In April, Joyce hit very well against RHP but struggled against LHP. He had a month of May where it didn't seem to matter if he was hitting against a RHP or a LHP. In June, Joyce began to struggle against RHP and had a higher OPS against LHP than he did against RHP. Joyce improved against RHP in July but really struggled against LHP. August has seen Joyce have a solid month against both RHP and LHP and he has a higher OPS against LHP.
The data provided is inconclusive as to whether or not Joyce hits well against LHP when he performs well against RHP or if he struggles against LHP when he struggles against RHP. The question remains whether or not Joyce can be an everyday RF for the Rays in the future but I am encouraged by Joyce's August performance and feel that his overall performance in 2011, an OPS of near .700, is adequate enough to garner most of the starts versus LHP in 2012.
I've included the month by month splits for 2008 and 2010 below for those interested.