Three of those five had something in common with the Cubs' young hitters in 2018.
Part of a hitting coach's job is helping young players develop. I don't see how they can justify keeping Chili Davis around.
Maybe he's the problem maybe he isn't. Here is their wRC+ under Chili
Mookie
2015 120
2016 136
Benintendi
2016 118 PA, 121
Bogaerts (pre Chili)
2013 50 PA, 85
2014 81
2015 (Chili) 111
2016 114
2017 injured wrist
Heck look at Harper 137, 115, 197, 111, 155, 135
Look at the Cubs this year guys Contreras, Rizzo, Bryant, Almora and Russell where the guys that fell off. 4/5 of those guys had injuries and or over use confirmed. The only guy that didn't is Almora and as bad as he played in the second half I wouldn't be shocked if he had something going on.
Happ was basically the same.
Baez, Zobrist, Heyward, Schwarber all improved over last year.
Development isn't linear.