Out of the 47 players who have 100 innings at 2b, Campbell's fielding percentage is 32nd. If you raise the innings limit to 200, he's 23rd out of 28. There's nothing about his glove that is major league average (-8 DRS, -3 ORS, -2 FRV). Campbell is NOT an MLB caliber SS even if he played it in HS like almost every other MLB IFer.
Marcelo Mayer fielding percentage at 3B is 1.000. He has a 0 DRS, 0 OAA overall.
Rafaela has a 602 OPS. No matter how good his defense is, that's not keeping him in a fulltime position.