Red Sox Canada

Why would the Red Sox not sign Pomeranz for $1.5 million + $3.5 million in roster and productivity bonuses. Seems like a no-brainer to me. Seems like so much upside and so little downside. I know he had a horrible 2018, but 2017 was awesome. W-L 17-6 and an ERA of 3.32. and a WHIP 1.353 and it wasn't luck. He has put up great numbers in his career. Either they are not confident he can return to form from last year's injuries, or he would rather pitch in a no pressure, smaller market. https://www.baseball-reference.com/players/p/pomerdr01.shtml