A human's core is one of the essential parts of his body; that's why it's called the core. Stuart Wallace of Beyond the Box Score describes it as "a complex swath of real estate, comprised of more muscles, ligaments, bones, and soft tissue elements than any other part of the body, with a number of systems that share portions of core anatomy to perform their duties, such as the genitourinary, gastrointestinal, and neurological systems."
Since the core is so important, any injury to the area could be debilitating, which is exactly what happened to Brad Boxberger. A pitcher's body is put under enough strain as is. Will a core injury affect him moving forward?
A previous example of a player dealing with a core injury would be Justin Verlander of the Tigers. In the same article, Wallace cites how Verlander's sports hernia hampered his delivery and caused strain in his shoulder, especially since Verlander utilizes a long stride with his plant foot. Wallace made the connection that as Verlander shortened his stride to compensate for his recovering core, he struggled to hit the bottom of the zone and his pitches rose.
Verlander and Boxberger are similar in that they pound the bottom of the zone. Looking below, you can see that in 2015, Boxberger primarily pitched to the bottom, right-handed side of the plate, jamming righties and forcing lefties to reach. In order to fully bounce back from his injury, Boxberger and the training staff will have to watch and see if Boxberger retains that same ability to attack the zone.
In addition, Verlander's fastball dropped almost a full tick in velocity from 2013 to 2014 (between which he had his sports hernia surgery). While it may not have been the full reason for his regression, there is the chance the two are related.
Along with location, Boxberger's game is predicated on his fastball-changeup combo. According to Brooks Baseball's pitchF/X, Boxberger's 2015 fastball averaged about 93.67 mph and his changeup averaged 80.76 mph. If Boxberger wants to continue suceeding on this combo, the velocity gap between the two pitches will have to stay. Verlander shows that Boxberger's velocity could drop due to the surgery, and it will be paramount that his fastball's speed remains as well.
While Boxberger's set timetable to return was about eight weeks from his surgery, it is undetermined when he will be fully recovered from his injury. He could conceivably be back with the team by the end of May, but if his location and velocity aren't at his usual levels, it could lead to serious struggles upon Boxberger's return.