Fangraphs in ranking him the Brewers 15th best prospect had this on him: "Phillips hit well in his small sample of big-league at-bats, slashing .276/.351/.448 and reaching on each of his five steal attempts. xStats, which calculates expected stats based on batted-ball data, suggests that this was a mirage, as does Phillips’ .408 BABIP.
Scouts aren’t sold on Phillips’ bat. He has a clunky leg kick and weight transfer that prevent him from turning on balls consistently, and he is violent about the head during his swing, exacerbating Phillips’ whiff-prone stiffness. He has struck out in 24% of his pro plate appearances and in 30% of his PAs the last two seasons. He projects as a 40 hitter, and his approach to contact will likely limit his game power output.
But he does lots of other things. Phillips is an above-average runner and high-effort player who makes it work in center field despite lacking great instincts. He has strong hands and is able to poke balls out the other way on occasion. Most notably, Phillips has elite, game-changing arm strength and uncorked a throw in excess of 104 mph, according to Statcast, this year. Some scouts think Phillips’ patience, raw power, and ability to play center field will make him an average everyday player, but most think his inability to hit will limit him to a lesser role."
That said, these questions about his bat should make him come cheaper in a trade. Possibly much cheaper than Santana.