The Phillies have a grand tradition of trying to make the slowest plodding players on the field play in the outfield. It started with an attempt to put Ryan Howard in left field to not have him be blocked by Jim Thome, and has continued to this day. Now some of this has been in the style of the original. Jim Thome is a Hall of Famer, and while Ryan Howard will never be a Hall of Famer, but he was one of the better offensive players in baseball for decent set of years. When the Phillies had Jonathan Singleton play left field in 2011, Ryan Howard was in his decline, but he still had a tiny nation’s GDP of future commitments in front of him. At the time Singleton was also a near consensus top 50 prospect and baseball and was coming off a year in which he hit .290/.393/.479 in low-A at age 18. Since then the Phillies have tried Darin Ruf in the outfield and Brock Stassi in the outfield, and at one point they attempted Tommy Joseph at third (which went predictably poorly). Now they have topped all of this off with Rhys Hoskins in left field.
Now Rhys Hoskins is a really good offensive prospect. I ranked him #5 in the system here on this website last week. He is hitting .280/.385/.570 in AAA with a sterling walk and strikeout rate and a Lehigh Valley record 27 home runs. He has probably been ready for the majors for a few months right now. He will also be 25 years old on opening day next year and needs to be added to the 40 man roster this offseason anyway, so it makes sense that the Phillies would like for him to play in the majors sooner rather than later.
The current Phillies first baseman is batting .249/.307/.440 on the season. Out of 27 qualified first basemen, that is the 26th wRC+ (god bless Mike Napoli), 21st in SLG, 26th in OBP, and 26th in fWAR. Tommy Joseph has been a great story, and for the second half of the 2016 season he showed flashes that he might actually be a good first basemen for the Phillies going forward. It is not hard to imagine Hoskins is a better first base option than Joseph (and if he isn’t they probably won’t be the future at the position for the Phillies).
The Phillies are obviously still wedded enough to Joseph to not move him out of the way for Hoskins or they already would have switched the two. Which is why we are getting Hoskins in the outfield. We have no sample on whether Hoskins will be any good out in left as he has not played the position since 2012 in his freshman year of college. What we do know is that he is a poor runner, with below average athleticism, and a solid arm. All of those factors point towards him being a well below average outfielder (and a large step down from the Nick Williams or Cam Perkins in left). Teams have a long history of running statues out in left field and pretending like their defensive value does not destroy their overall upside (see Kemp, Matt and his .290/.336/.477 0 WAR season). The Phillies aren’t going anywhere this year, so on the surface wins and losses don’t make too much difference to this team.
The problem is developmental. The Phillies have a bunch of young pitching in the majors, and possibly another young starter on the way to take Jake Thompson’s spot in the rotation. Ideally the Phillies want to put these pitchers in a place to succeed. The only problem is the Phillies pitching staff is terrible at generating ground balls. The only two who did it at a high level are Aaron Nola and Luis Garcia. The team as a whole has the 25th best ground ball rate in baseball at 41.9%. That means a long of balls into the outfield and a lot more chance for a bad fielder to cause poor plays. The Phillies pitchers are also fairly inefficient and the overall talent level is not great on a night to night basis. Adding a poor fielder is going to cause harm to their ability to perform at a high level, and potentially could overtax and an already poor and overtaxed bullpen.
We already know the trade interest in Tommy Joseph is non-existent, and it is likely to remain that way given the current offensive climate. To protect their minuscule potential trade return for him, the Phillies are willing to sacrifice the development of their young pitching. Their experiment starts tonight.