Brandon Morrow has a career ERA 0.24 higher than his xFIP. BABIP is league average. HR/FB is league average. So we're talking about a hair less than a quarter of a run per 9 innings over a relatively small sample (769 innings). That equates to approximately 20 runs over his career. Brandon Morrow, xFIP buster extraordinaire, has under-performed his xFIP by about 20 runs in his career. DRS has him as a very poor defensive pitcher at -7 runs. There are error bars on that, so we'll call it 5-10. That means that in 769 innings, the totality of Brandon Morrow's xFIP breaking-ness is somewhere in the vicinity of 10-15 runs.
What's more likely:
1) the many things outside his control (luck, sos, team defense) have combined to cause a minuscule 10-15-run discrepancy between his xFIP and FIP (that's one run every 60 innings or so)
2) his ERA is his true talent, and that 10-15 run discrepancy over almost 800 innings speaks volumes about his abilities as a pitcher.
Anyone with even the smallest shred of sensibility should default to the 'eh, there's probably nothing there' position. Because the discrepancy is small, and many, many factors are at play.