Gil could and would start at second base, or third base, or short, whatever the Yankees most needed that season, or indeed that day, and he was a wonderful fielder at all three positions. Baseball-reference's Fielding Runs (based on Sean Smith's Total Zone fielding evaluation system) gives McDougald the fourth highest total among Yankee infielders all-time, behind only Clete Boyer, Phil Rizzuto,and Joe Gordon. But Boyer, Rizzuto and Gordon each played only one infield position (third, short and second, respectively), while McDougald mastered all three of their positions and thus gave the Yankees an extraordinary amount of flexibility to deploy their infield talent effectively throughout the 1950s.
And McDougald was a legitimate offensive force as well. Clete Boyer was one of the great defensive third basemen of all time, but had a career OPS+ of only 86, and Rizzuto's career OPS+ was 93, good for a shortstop of his (or any) era, but not what you call a big hitter. McDougald was nearly as valuable a fielder as either Clete or Phil, but Gil's career OPS+ was a quite substantial 111 (comparable to, say, Alfonso Soriano's career 113 OPS+), making him an important part of the Yankee lineup wherever he played in the infield.
Truly one of the great all-around talents the majors has seen. He retired early, playing only until he was 32, retiring as a Yankee rather than leave in the expansion draft to go play for the brand new Los Angeles Angels. As a result his career numbers don't stack up with the greatest. But he was enormously valuable to the Yankees. McDougald's nickname among his teammates, according to Don Larsen's book The Perfect Yankee, was "Smash", and he was indeed a smashing success.