By dWAR, this isn't the case.Manny Ramirez's teams were almost always good, usually very good, with him playing the outfield and rarely DH-ing. Like almost every year he played more than half the games, his teams were finished in first or second place and won a ton of games.
Of course an individual player isn't directly responsible for his team's success, and his bat helped make up for some defensive issues.
But defensive stats (especially the ones that are a decade or two old) and player reputations are really not very revealing either. For example, for a lot of the years Manny was with the Red Sox, some of the stats didn't account for the impact of the LF wall correctly. They would ding the LF for not catching short fly balls that hit the wall, because they would have been outs in other parks, so it must be the LF's fault when a 320-foot pop fly hits 15 feet high off the wall.
I remember a year after the trade, somehow Jason Bay's defensive stats cratered as soon as he moved to Fenway, while Manny's improved as soon as he left Fenway. Then Bay's numbers bounced up again when he left Boston. Surely just a coincidence, as those defensive numbers were the best we had at the time, so that means they were correct, right?
And I think part of Manny's bad defensive rep came from some of his fielding mistakes being legendarily hilarious.
(This all was pretty much just an excuse to post this video):
View: https://www.youtube.com/watch?v=wcewudvPjdM
Bay's previous 4 seasons before Boston-
-1.4
-.08
-1.7
-1.4
Sox-
0.1 (best of career)
-0.3
Post Sox-
-0.1
-0.7
Manny- Averaged
-.98 with Cleveland
-1.4 with Boston
-1.0 With LA (small sample).
I think he played LF at Fenway pretty well, all things considered and his rep was off from reality (and also dWAR is flawed).