Hard for me to expect much of him based on his last three seasons, especially if his best defensive positions are the ones we don't need (i.e. middle IF). The samples are too small to make much of the WAR (case in point, Sean Rodriguez, who I think was 0.5 BBRef WAR just a few weeks ago and is now down to -0.1). But he's younger than Rodriguez (who I'm assuming sticks around though I guess they do overlap quite a bit).
It's a flier, he could also be gone in four weeks.
Miller, 29, hit a career-high 30 home runs for the Rays in 2016, but he has hit 17 homers in parts of three seasons since with the Rays, Brewers and Indians. He posted a .692 OPS in that span. Miller has a .755 career OPS against right-handed pitchers, which would be welcomed production for the Phillies, but he also has a .412 career OPS as a pinch-hitter.
Of course you can't make much of PH stats either way.