Rickey puts up comparable offensive stats to Mattingly, and plays a position where it's very difficult to find a guy to put up stats like that. Rickey also got 70 extra bases (80 steals, 10 CS) with his legs, and that doesn't take into consideration the first to third and first to home on a double, etc. I was also under the impression that Rickey was an above-average fielder in his 20s. I didn't see him play then, but that was my assumption. I'd argue if you took Rickey off that team, they'd lose more games than if you took Mattingly.
Now, if you're going to tell me that Rickey was a selfish ***** that rubbed people the wrong way, and Mattingly was the professional and leader of that ballclub? Maybe that's true, it's not something that can be measured. I tend to think things that like are overstated in baseball, but it's an argument.