Shortstop - George Davis: 44.6 WAR
It was somewhat surprising to see Brandon Crawford outside the top 3 at shortstop, but George Davis took home a very tight race for the top spot with his 44.6 rWAR from 1893 to 1903. His .860 OPS in over 4,800 plate appearances is pretty impressive when you consider he only hit 53 homers. Stealing 357 bases and putting up a .332 batting average helped the cause there.
In second place, Travis Jackson just missed out on the starting shortstop spot with 44.2 rWAR for his work from 1922-1936. His 6,682 plate appearances with the Giants remains the most of any Giants shortstop by a significant margin over Crawford. Art Fletcher comes in third with 42.3 rWAR from 1909 to 1920.
Third Base - Matt Williams: 34.1 WAR
With just a 0.1 rWAR margin, Matt Williams won the Giants' starting third baseman spot here with 34.1 rWAR from 1987 to 1996. Williams obviously would have had a much more comfortable margin if the baseball strike hadn't happened and he did put up some real numbers for Arizona later in his career as well.
Just behind Williams is Art Devlin who played for the Giants from 1904 to 1911 at 34.0 rWAR. Comparing Williams to a guy with 10 home runs in a Giants uniform is pretty funny, but Devlin did steal 266 bases and Baseball-Reference liked him defensively. The bronze goes to Jim Ray Hart with his 25.1 rWAR from 1963 to 1973. For those wondering, Pablo Sandoval's 20.8 rWAR came in seventh.
Left Field - Barry Bonds: 112.5 WAR
This one is no surprise and was not even remotely close as Barry Bonds' staggering 112.5 rWAR with the Giants more than tripled the second place finisher. All of the PED speculation and controversy aside, what Bonds did on the baseball field is the stuff of legends. He broke records that are very unlikely to ever be broken and his 1.143 OPS during his time with the Giants is just absurd. Just put him in Cooperstown already.
The poor soul in second place for left field is George Burns whose 36.4 rWAR from 1911 to 1921 is dwarfed by Bonds. There is another pretty substantial drop-off to third place with Kevin Mitchell's 19.2 rWAR from 1987 to 1991.