I commented on this -- specifically about base stealing, because the numbers were readily available -- during the season, but the difference between Paul Molitor the base runner and the team Paul Molitor managed in 2015 was remarkable.
Molitor's baserunning savvy was legendary. He was fast, certainly, but that was only part of it. He was aware and aggressive. He stole bases, and took extra bases, with extraordinary efficiency.
The 2015 Twins, not so much. And the quality of Minnesota's baserunning, as a team, was sharply lower than under Ron Gardenhire.
From the Bill James Handbooks, as compiled by Baseball Info Systems:
2013: Twins had an overall net gain of +30. They were +44 running the bases, -13 as base stealers. The base running score was third highest in baseball that year.
2014: Total, +109. On the bases, +82; stealing, +27. The total was second in baseball, the base running component first.
2015: Total, - 19. On the bases, -13, stealing, -6. Only seven teams had lower total scores.
Molitor had no connection to the major league team in 2013. In 2014 he was on the coaching staff and baserunning was a specific part of his portfolio. As manager in 2015, he doubtless delegated at least part of that aspect. But that's a stiff decline.