Fangraphs makes a case that both Moustakas' defense and foot speed may have dropped off a cliff after his torn ACL in 2016, one wonders if Boras had aimed in the $40-$50M range initially, if maybe he would have gotten more nibbles.
"Statcast can come in handy here. We can look at sprint speeds, from
Baseball Savant. In 2015, Moustakas’ average sprint speed ranked in the 38th percentile, and the 48th percentile among third basemen. In 2017, however, Moustakas’ average sprint speed ranked in the 7th percentile, and the 9th percentile among third basemen. Suddenly, Moustakas was moving slower, and it’s evident in his baserunning measures. In terms of moving up an extra base on hits, Moustakas just ranked in the lowest percentile. Moving from first to third on singles, Moustakas ranked in the lowest percentile. Moving from first to home on doubles, he ranked in the 3rd percentile. Moving from second to home on singles, he ranked in the 14th percentile. Moustakas, in 2017, didn’t attempt a single stolen base. Moustakas did very little running.
And that wasn’t the only casualty. Looking at third basemen between 2014 and 2016, and blending both DRS and UZR, Moustakas’ defense ranked in the 64th percentile. This past season, again among third basemen, his defense ranked in the 23rd percentile. Moustakas came back, and he hit. He hit a bunch of home runs. But while that was happening, Moustakas had slowed down. He was playing worse defense, at least statistically, and the Royals started him 17 times at DH."
https://www.fangraphs.com/blogs/why-mike-moustakas-market-didnt-develop/